1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2012 by Delphix. All rights reserved.
  24  */
  25 
  26 /*
  27  * The System Duty Cycle (SDC) scheduling class
  28  * --------------------------------------------
  29  *
  30  * Background
  31  *
  32  * Kernel threads in Solaris have traditionally not been large consumers
  33  * of CPU time.  They typically wake up, perform a small amount of
  34  * work, then go back to sleep waiting for either a timeout or another
  35  * signal.  On the assumption that the small amount of work that they do
  36  * is important for the behavior of the whole system, these threads are
  37  * treated kindly by the dispatcher and the SYS scheduling class: they run
  38  * without preemption from anything other than real-time and interrupt
  39  * threads; when preempted, they are put at the front of the queue, so they
  40  * generally do not migrate between CPUs; and they are allowed to stay
  41  * running until they voluntarily give up the CPU.
  42  *
  43  * As Solaris has evolved, new workloads have emerged which require the
  44  * kernel to perform significant amounts of CPU-intensive work.  One
  45  * example of such a workload is ZFS's transaction group sync processing.
  46  * Each sync operation generates a large batch of I/Os, and each I/O
  47  * may need to be compressed and/or checksummed before it is written to
  48  * storage.  The taskq threads which perform the compression and checksums
  49  * will run nonstop as long as they have work to do; a large sync operation
  50  * on a compression-heavy dataset can keep them busy for seconds on end.
  51  * This causes human-time-scale dispatch latency bubbles for any other
  52  * threads which have the misfortune to share a CPU with the taskq threads.
  53  *
  54  * The SDC scheduling class is a solution to this problem.
  55  *
  56  *
  57  * Overview
  58  *
  59  * SDC is centered around the concept of a thread's duty cycle (DC):
  60  *
  61  *                            ONPROC time
  62  *      Duty Cycle =    ----------------------
  63  *                      ONPROC + Runnable time
  64  *
  65  * This is the ratio of the time that the thread spent running on a CPU
  66  * divided by the time it spent running or trying to run.  It is unaffected
  67  * by any time the thread spent sleeping, stopped, etc.
  68  *
  69  * A thread joining the SDC class specifies a "target" DC that it wants
  70  * to run at.  To implement this policy, the routine sysdc_update() scans
  71  * the list of active SDC threads every few ticks and uses each thread's
  72  * microstate data to compute the actual duty cycle that that thread
  73  * has experienced recently.  If the thread is under its target DC, its
  74  * priority is increased to the maximum available (sysdc_maxpri, which is
  75  * 99 by default).  If the thread is over its target DC, its priority is
  76  * reduced to the minimum available (sysdc_minpri, 0 by default).  This
  77  * is a fairly primitive approach, in that it doesn't use any of the
  78  * intermediate priorities, but it's not completely inappropriate.  Even
  79  * though threads in the SDC class might take a while to do their job, they
  80  * are by some definition important if they're running inside the kernel,
  81  * so it is reasonable that they should get to run at priority 99.
  82  *
  83  * If a thread is running when sysdc_update() calculates its actual duty
  84  * cycle, and there are other threads of equal or greater priority on its
  85  * CPU's dispatch queue, sysdc_update() preempts that thread.  The thread
  86  * acknowledges the preemption by calling sysdc_preempt(), which calls
  87  * setbackdq(), which gives other threads with the same priority a chance
  88  * to run.  This creates a de facto time quantum for threads in the SDC
  89  * scheduling class.
  90  *
  91  * An SDC thread which is assigned priority 0 can continue to run if
  92  * nothing else needs to use the CPU that it's running on.  Similarly, an
  93  * SDC thread at priority 99 might not get to run as much as it wants to
  94  * if there are other priority-99 or higher threads on its CPU.  These
  95  * situations would cause the thread to get ahead of or behind its target
  96  * DC; the longer the situations lasted, the further ahead or behind the
  97  * thread would get.  Rather than condemning a thread to a lifetime of
  98  * paying for its youthful indiscretions, SDC keeps "base" values for
  99  * ONPROC and Runnable times in each thread's sysdc data, and updates these
 100  * values periodically.  The duty cycle is then computed using the elapsed
 101  * amount of ONPROC and Runnable times since those base times.
 102  *
 103  * Since sysdc_update() scans SDC threads fairly frequently, it tries to
 104  * keep the list of "active" threads small by pruning out threads which
 105  * have been asleep for a brief time.  They are not pruned immediately upon
 106  * going to sleep, since some threads may bounce back and forth between
 107  * sleeping and being runnable.
 108  *
 109  *
 110  * Interfaces
 111  *
 112  * void sysdc_thread_enter(t, dc, flags)
 113  *
 114  *      Moves a kernel thread from the SYS scheduling class to the
 115  *      SDC class. t must have an associated LWP (created by calling
 116  *      lwp_kernel_create()).  The thread will have a target DC of dc.
 117  *      Flags should be either 0 or SYSDC_THREAD_BATCH.  If
 118  *      SYSDC_THREAD_BATCH is specified, the thread is expected to be
 119  *      doing large amounts of processing.
 120  *
 121  *
 122  * Complications
 123  *
 124  * - Run queue balancing
 125  *
 126  *      The Solaris dispatcher is biased towards letting a thread run
 127  *      on the same CPU which it last ran on, if no more than 3 ticks
 128  *      (i.e. rechoose_interval) have passed since the thread last ran.
 129  *      This helps to preserve cache warmth.  On the other hand, it also
 130  *      tries to keep the per-CPU run queues fairly balanced; if the CPU
 131  *      chosen for a runnable thread has a run queue which is three or
 132  *      more threads longer than a neighboring CPU's queue, the runnable
 133  *      thread is dispatched onto the neighboring CPU instead.
 134  *
 135  *      These policies work well for some workloads, but not for many SDC
 136  *      threads.  The taskq client of SDC, for example, has many discrete
 137  *      units of work to do.  The work units are largely independent, so
 138  *      cache warmth is not an important consideration.  It is important
 139  *      that the threads fan out quickly to different CPUs, since the
 140  *      amount of work these threads have to do (a few seconds worth at a
 141  *      time) doesn't leave much time to correct thread placement errors
 142  *      (i.e. two SDC threads being dispatched to the same CPU).
 143  *
 144  *      To fix this, SDC uses the TS_RUNQMATCH flag introduced for FSS.
 145  *      This tells the dispatcher to keep neighboring run queues' lengths
 146  *      more evenly matched, which allows SDC threads to migrate more
 147  *      easily.
 148  *
 149  * - LWPs and system processes
 150  *
 151  *      SDC can only be used for kernel threads.  Since SDC uses microstate
 152  *      accounting data to compute each thread's actual duty cycle, all
 153  *      threads entering the SDC class must have associated LWPs (which
 154  *      store the microstate data).  This means that the threads have to
 155  *      be associated with an SSYS process, i.e. one created by newproc().
 156  *      If the microstate accounting information is ever moved into the
 157  *      kthread_t, this restriction could be lifted.
 158  *
 159  * - Dealing with oversubscription
 160  *
 161  *      Since SDC duty cycles are per-thread, it is possible that the
 162  *      aggregate requested duty cycle of all SDC threads in a processor
 163  *      set could be greater than the total CPU time available in that set.
 164  *      The FSS scheduling class has an analogous situation, which it deals
 165  *      with by reducing each thread's allotted CPU time proportionally.
 166  *      Since SDC doesn't need to be as precise as FSS, it uses a simpler
 167  *      solution to the oversubscription problem.
 168  *
 169  *      sysdc_update() accumulates the amount of time that max-priority SDC
 170  *      threads have spent on-CPU in each processor set, and uses that sum
 171  *      to create an implied duty cycle for that processor set:
 172  *
 173  *                              accumulated CPU time
 174  *         pset DC =    -----------------------------------
 175  *                       (# CPUs) * time since last update
 176  *
 177  *      If this implied duty cycle is above a maximum pset duty cycle (90%
 178  *      by default), sysdc_update() sets the priority of all SDC threads
 179  *      in that processor set to sysdc_minpri for a "break" period.  After
 180  *      the break period, it waits for a "nobreak" period before trying to
 181  *      enforce the pset duty cycle limit again.
 182  *
 183  * - Processor sets
 184  *
 185  *      As the above implies, SDC is processor set aware, but it does not
 186  *      currently allow threads to change processor sets while in the SDC
 187  *      class.  Instead, those threads must join the desired processor set
 188  *      before entering SDC. [1]
 189  *
 190  * - Batch threads
 191  *
 192  *      A thread joining the SDC class can specify the SDC_THREAD_BATCH
 193  *      flag.  This flag currently has no effect, but marks threads which
 194  *      do bulk processing.
 195  *
 196  * - t_kpri_req
 197  *
 198  *      The TS and FSS scheduling classes pay attention to t_kpri_req,
 199  *      which provides a simple form of priority inheritance for
 200  *      synchronization primitives (such as rwlocks held as READER) which
 201  *      cannot be traced to a unique thread.  The SDC class does not honor
 202  *      t_kpri_req, for a few reasons:
 203  *
 204  *      1.  t_kpri_req is notoriously inaccurate.  A measure of its
 205  *          inaccuracy is that it needs to be cleared every time a thread
 206  *          returns to user mode, because it is frequently non-zero at that
 207  *          point.  This can happen because "ownership" of synchronization
 208  *          primitives that use t_kpri_req can be silently handed off,
 209  *          leaving no opportunity to will the t_kpri_req inheritance.
 210  *
 211  *      2.  Unlike in TS and FSS, threads in SDC *will* eventually run at
 212  *          kernel priority.  This means that even if an SDC thread
 213  *          is holding a synchronization primitive and running at low
 214  *          priority, its priority will eventually be raised above 60,
 215  *          allowing it to drive on and release the resource.
 216  *
 217  *      3.  The first consumer of SDC uses the taskq subsystem, which holds
 218  *          a reader lock for the duration of the task's execution.  This
 219  *          would mean that SDC threads would never drop below kernel
 220  *          priority in practice, which defeats one of the purposes of SDC.
 221  *
 222  * - Why not FSS?
 223  *
 224  *      It might seem that the existing FSS scheduling class could solve
 225  *      the problems that SDC is attempting to solve.  FSS's more precise
 226  *      solution to the oversubscription problem would hardly cause
 227  *      trouble, as long as it performed well.  SDC is implemented as
 228  *      a separate scheduling class for two main reasons: the initial
 229  *      consumer of SDC does not map well onto the "project" abstraction
 230  *      that is central to FSS, and FSS does not expect to run at kernel
 231  *      priorities.
 232  *
 233  *
 234  * Tunables
 235  *
 236  * - sysdc_update_interval_msec:  Number of milliseconds between
 237  *      consecutive thread priority updates.
 238  *
 239  * - sysdc_reset_interval_msec:  Number of milliseconds between
 240  *      consecutive resets of a thread's base ONPROC and Runnable
 241  *      times.
 242  *
 243  * - sysdc_prune_interval_msec:  Number of milliseconds of sleeping
 244  *      before a thread is pruned from the active list.
 245  *
 246  * - sysdc_max_pset_DC:  Allowable percentage of a processor set's
 247  *      CPU time which SDC can give to its high-priority threads.
 248  *
 249  * - sysdc_break_msec:  Number of milliseconds of "break" taken when
 250  *      sysdc_max_pset_DC is exceeded.
 251  *
 252  *
 253  * Future work (in SDC and related subsystems)
 254  *
 255  * - Per-thread rechoose interval (0 for SDC)
 256  *
 257  *      Allow each thread to specify its own rechoose interval.  SDC
 258  *      threads would specify an interval of zero, which would rechoose
 259  *      the CPU with the lowest priority once per update.
 260  *
 261  * - Allow threads to change processor sets after joining the SDC class
 262  *
 263  * - Thread groups and per-group DC
 264  *
 265  *      It might be nice to be able to specify a duty cycle which applies
 266  *      to a group of threads in aggregate.
 267  *
 268  * - Per-group DC callback to allow dynamic DC tuning
 269  *
 270  *      Currently, DCs are assigned when the thread joins SDC.  Some
 271  *      workloads could benefit from being able to tune their DC using
 272  *      subsystem-specific knowledge about the workload.
 273  *
 274  * - Finer-grained priority updates
 275  *
 276  * - More nuanced management of oversubscription
 277  *
 278  * - Moving other CPU-intensive threads into SDC
 279  *
 280  * - Move msacct data into kthread_t
 281  *
 282  *      This would allow kernel threads without LWPs to join SDC.
 283  *
 284  *
 285  * Footnotes
 286  *
 287  * [1] The details of doing so are left as an exercise for the reader.
 288  */
 289 
 290 #include <sys/types.h>
 291 #include <sys/sysdc.h>
 292 #include <sys/sysdc_impl.h>
 293 
 294 #include <sys/class.h>
 295 #include <sys/cmn_err.h>
 296 #include <sys/cpuvar.h>
 297 #include <sys/cpupart.h>
 298 #include <sys/debug.h>
 299 #include <sys/disp.h>
 300 #include <sys/errno.h>
 301 #include <sys/inline.h>
 302 #include <sys/kmem.h>
 303 #include <sys/modctl.h>
 304 #include <sys/schedctl.h>
 305 #include <sys/sdt.h>
 306 #include <sys/sunddi.h>
 307 #include <sys/sysmacros.h>
 308 #include <sys/systm.h>
 309 #include <sys/var.h>
 310 
 311 /*
 312  * Tunables - loaded into the internal state at module load time
 313  */
 314 uint_t          sysdc_update_interval_msec = 20;
 315 uint_t          sysdc_reset_interval_msec = 400;
 316 uint_t          sysdc_prune_interval_msec = 100;
 317 uint_t          sysdc_max_pset_DC = 90;
 318 uint_t          sysdc_break_msec = 80;
 319 
 320 /*
 321  * Internal state - constants set up by sysdc_initparam()
 322  */
 323 static clock_t  sysdc_update_ticks;     /* ticks between updates */
 324 static uint_t   sysdc_prune_updates;    /* updates asleep before pruning */
 325 static uint_t   sysdc_reset_updates;    /* # of updates before reset */
 326 static uint_t   sysdc_break_updates;    /* updates to break */
 327 static uint_t   sysdc_nobreak_updates;  /* updates to not check */
 328 static uint_t   sysdc_minDC;            /* minimum allowed DC */
 329 static uint_t   sysdc_maxDC;            /* maximum allowed DC */
 330 static pri_t    sysdc_minpri;           /* minimum allowed priority */
 331 static pri_t    sysdc_maxpri;           /* maximum allowed priority */
 332 
 333 /*
 334  * Internal state
 335  */
 336 static kmutex_t sysdc_pset_lock;        /* lock protecting pset data */
 337 static list_t   sysdc_psets;            /* list of psets with SDC threads */
 338 static uint_t   sysdc_param_init;       /* sysdc_initparam() has been called */
 339 static uint_t   sysdc_update_timeout_started; /* update timeout is active */
 340 static hrtime_t sysdc_last_update;      /* time of last sysdc_update() */
 341 static sysdc_t  sysdc_dummy;            /* used to terminate active lists */
 342 
 343 /*
 344  * Internal state - active hash table
 345  */
 346 #define SYSDC_NLISTS    8
 347 #define SYSDC_HASH(sdc) (((uintptr_t)(sdc) >> 6) & (SYSDC_NLISTS - 1))
 348 static sysdc_list_t     sysdc_active[SYSDC_NLISTS];
 349 #define SYSDC_LIST(sdc)         (&sysdc_active[SYSDC_HASH(sdc)])
 350 
 351 #ifdef DEBUG
 352 static struct {
 353         uint64_t        sysdc_update_times_asleep;
 354         uint64_t        sysdc_update_times_base_ran_backwards;
 355         uint64_t        sysdc_update_times_already_done;
 356         uint64_t        sysdc_update_times_cur_ran_backwards;
 357         uint64_t        sysdc_compute_pri_breaking;
 358         uint64_t        sysdc_activate_enter;
 359         uint64_t        sysdc_update_enter;
 360         uint64_t        sysdc_update_exited;
 361         uint64_t        sysdc_update_not_sdc;
 362         uint64_t        sysdc_update_idle;
 363         uint64_t        sysdc_update_take_break;
 364         uint64_t        sysdc_update_no_psets;
 365         uint64_t        sysdc_tick_not_sdc;
 366         uint64_t        sysdc_tick_quantum_expired;
 367         uint64_t        sysdc_thread_enter_enter;
 368 } sysdc_stats;
 369 
 370 #define SYSDC_INC_STAT(x)       (sysdc_stats.x++)
 371 #else
 372 #define SYSDC_INC_STAT(x)       ((void)0)
 373 #endif
 374 
 375 /* macros are UPPER CASE */
 376 #define HOWMANY(a, b)   howmany((a), (b))
 377 #define MSECTOTICKS(a)  HOWMANY((a) * 1000, usec_per_tick)
 378 
 379 static void
 380 sysdc_initparam(void)
 381 {
 382         uint_t sysdc_break_ticks;
 383 
 384         /* update / prune intervals */
 385         sysdc_update_ticks = MSECTOTICKS(sysdc_update_interval_msec);
 386 
 387         sysdc_prune_updates = HOWMANY(sysdc_prune_interval_msec,
 388             sysdc_update_interval_msec);
 389         sysdc_reset_updates = HOWMANY(sysdc_reset_interval_msec,
 390             sysdc_update_interval_msec);
 391 
 392         /* We must get at least a little time on CPU. */
 393         sysdc_minDC = 1;
 394         sysdc_maxDC = SYSDC_DC_MAX;
 395         sysdc_minpri = 0;
 396         sysdc_maxpri = maxclsyspri;
 397 
 398         /* break parameters */
 399         if (sysdc_max_pset_DC > SYSDC_DC_MAX) {
 400                 sysdc_max_pset_DC = SYSDC_DC_MAX;
 401         }
 402         sysdc_break_ticks = MSECTOTICKS(sysdc_break_msec);
 403         sysdc_break_updates = HOWMANY(sysdc_break_ticks, sysdc_update_ticks);
 404 
 405         /*
 406          * We want:
 407          *
 408          *      sysdc_max_pset_DC = (nobreak / (break + nobreak))
 409          *
 410          *      ==>    nobreak = sysdc_max_pset_DC * (break + nobreak)
 411          *
 412          *                          sysdc_max_pset_DC * break
 413          *      ==>    nobreak = -------------------------
 414          *                          1 - sysdc_max_pset_DC
 415          */
 416         sysdc_nobreak_updates =
 417             HOWMANY((uint64_t)sysdc_break_updates * sysdc_max_pset_DC,
 418             (SYSDC_DC_MAX - sysdc_max_pset_DC));
 419 
 420         sysdc_param_init = 1;
 421 }
 422 
 423 #undef HOWMANY
 424 #undef MSECTOTICKS
 425 
 426 #define SDC_UPDATE_INITIAL      0x1     /* for the initial update */
 427 #define SDC_UPDATE_TIMEOUT      0x2     /* from sysdc_update() */
 428 #define SDC_UPDATE_TICK         0x4     /* from sysdc_tick(), on expiry */
 429 
 430 /*
 431  * Updates the recorded times in the sdc, and returns the elapsed ONPROC
 432  * and Runnable times since the last reset.
 433  *
 434  * newO is the thread's actual ONPROC time; it's used during sysdc_update()
 435  * to track processor set usage.
 436  */
 437 static void
 438 sysdc_update_times(sysdc_t *sdc, uint_t flags,
 439     hrtime_t *O, hrtime_t *R, hrtime_t *newO)
 440 {
 441         kthread_t *const t = sdc->sdc_thread;
 442         const uint_t    initial = (flags & SDC_UPDATE_INITIAL);
 443         const uint_t    update = (flags & SDC_UPDATE_TIMEOUT);
 444         const clock_t   now = ddi_get_lbolt();
 445         uint_t          do_reset;
 446 
 447         ASSERT(THREAD_LOCK_HELD(t));
 448 
 449         *O = *R = 0;
 450 
 451         /* If we've been sleeping, we know we haven't had any ONPROC time. */
 452         if (sdc->sdc_sleep_updates != 0 &&
 453             sdc->sdc_sleep_updates != sdc->sdc_nupdates) {
 454                 *newO = sdc->sdc_last_base_O;
 455                 SYSDC_INC_STAT(sysdc_update_times_asleep);
 456                 return;
 457         }
 458 
 459         /*
 460          * If this is our first update, or we've hit the reset point,
 461          * we need to reset our base_{O,R}.  Once we've updated them, we
 462          * report O and R for the entire prior interval.
 463          */
 464         do_reset = initial;
 465         if (update) {
 466                 ++sdc->sdc_nupdates;
 467                 if ((sdc->sdc_nupdates % sysdc_reset_updates) == 0)
 468                         do_reset = 1;
 469         }
 470         if (do_reset) {
 471                 hrtime_t baseO, baseR;
 472                 if (initial) {
 473                         /*
 474                          * Start off our cycle count somewhere in the middle,
 475                          * to keep the resets from all happening at once.
 476                          *
 477                          * 4999 is a handy prime much larger than
 478                          * sysdc_reset_updates, so that we don't run into
 479                          * trouble if the resolution is a multiple of
 480                          * sysdc_reset_updates.
 481                          */
 482                         sdc->sdc_nupdates = (uint_t)((gethrtime() % 4999) %
 483                             sysdc_reset_updates);
 484                         baseO = baseR = 0;
 485                 } else {
 486                         baseO = sdc->sdc_base_O;
 487                         baseR = sdc->sdc_base_R;
 488                 }
 489 
 490                 mstate_systhread_times(t, &sdc->sdc_base_O, &sdc->sdc_base_R);
 491                 *newO = sdc->sdc_base_O;
 492 
 493                 sdc->sdc_reset = now;
 494                 sdc->sdc_pri_check = -1; /* force mismatch below */
 495 
 496                 /*
 497                  * See below for rationale.
 498                  */
 499                 if (baseO > sdc->sdc_base_O || baseR > sdc->sdc_base_R) {
 500                         SYSDC_INC_STAT(sysdc_update_times_base_ran_backwards);
 501                         baseO = sdc->sdc_base_O;
 502                         baseR = sdc->sdc_base_R;
 503                 }
 504 
 505                 /* compute based on the entire interval */
 506                 *O = (sdc->sdc_base_O - baseO);
 507                 *R = (sdc->sdc_base_R - baseR);
 508                 return;
 509         }
 510 
 511         /*
 512          * If we're called from sysdc_update(), we *must* return a value
 513          * for newO, so we always call mstate_systhread_times().
 514          *
 515          * Otherwise, if we've already done a pri check this tick,
 516          * we can skip it.
 517          */
 518         if (!update && sdc->sdc_pri_check == now) {
 519                 SYSDC_INC_STAT(sysdc_update_times_already_done);
 520                 return;
 521         }
 522 
 523         /* Get the current times from the thread */
 524         sdc->sdc_pri_check = now;
 525         mstate_systhread_times(t, &sdc->sdc_cur_O, &sdc->sdc_cur_R);
 526         *newO = sdc->sdc_cur_O;
 527 
 528         /*
 529          * The updating of microstate accounting is not done under a
 530          * consistent set of locks, particularly the t_waitrq field.  This
 531          * can lead to narrow windows in which we account for time in the
 532          * wrong bucket, which on the next read will be accounted for
 533          * correctly.
 534          *
 535          * If our sdc_base_* fields were affected by one of these blips, we
 536          * throw away the old data, and pretend this tick didn't happen.
 537          */
 538         if (sdc->sdc_cur_O < sdc->sdc_base_O ||
 539             sdc->sdc_cur_R < sdc->sdc_base_R) {
 540 
 541                 sdc->sdc_base_O = sdc->sdc_cur_O;
 542                 sdc->sdc_base_R = sdc->sdc_cur_R;
 543 
 544                 SYSDC_INC_STAT(sysdc_update_times_cur_ran_backwards);
 545                 return;
 546         }
 547 
 548         *O = sdc->sdc_cur_O - sdc->sdc_base_O;
 549         *R = sdc->sdc_cur_R - sdc->sdc_base_R;
 550 }
 551 
 552 /*
 553  * sysdc_compute_pri()
 554  *
 555  *      Recomputes the priority of the thread, leaving the result in
 556  *      sdc->sdc_epri.  Returns 1 if a priority update should occur
 557  *      (which will also trigger a cpu_surrender()), otherwise
 558  *      returns 0.
 559  */
 560 static uint_t
 561 sysdc_compute_pri(sysdc_t *sdc, uint_t flags)
 562 {
 563         kthread_t *const t = sdc->sdc_thread;
 564         const uint_t    update = (flags & SDC_UPDATE_TIMEOUT);
 565         const uint_t    tick = (flags & SDC_UPDATE_TICK);
 566 
 567         hrtime_t        O, R;
 568         hrtime_t        newO = -1;
 569 
 570         ASSERT(THREAD_LOCK_HELD(t));
 571 
 572         sysdc_update_times(sdc, flags, &O, &R, &newO);
 573         ASSERT(!update || newO != -1);
 574 
 575         /* If we have new data, recompute our priority. */
 576         if ((O + R) != 0) {
 577                 sdc->sdc_cur_DC = (O * SYSDC_DC_MAX) / (O + R);
 578 
 579                 /* Adjust our priority to move our DC closer to the target. */
 580                 if (sdc->sdc_cur_DC < sdc->sdc_target_DC)
 581                         sdc->sdc_pri = sdc->sdc_maxpri;
 582                 else
 583                         sdc->sdc_pri = sdc->sdc_minpri;
 584         }
 585 
 586         /*
 587          * If our per-pset duty cycle goes over the max, we will take a break.
 588          * This forces all sysdc threads in the pset to minimum priority, in
 589          * order to let everyone else have a chance at the CPU.
 590          */
 591         if (sdc->sdc_pset->sdp_need_break) {
 592                 SYSDC_INC_STAT(sysdc_compute_pri_breaking);
 593                 sdc->sdc_epri = sdc->sdc_minpri;
 594         } else {
 595                 sdc->sdc_epri = sdc->sdc_pri;
 596         }
 597 
 598         DTRACE_PROBE4(sysdc__compute__pri,
 599             kthread_t *, t, pri_t, sdc->sdc_epri, uint_t, sdc->sdc_cur_DC,
 600             uint_t, sdc->sdc_target_DC);
 601 
 602         /*
 603          * For sysdc_update(), we compute the ONPROC time for high-priority
 604          * threads, which is used to calculate the per-pset duty cycle.  We
 605          * will always tell our callers to update the thread's priority,
 606          * since we want to force a cpu_surrender().
 607          *
 608          * We reset sdc_update_ticks so that sysdc_tick() will only update
 609          * the thread's priority if our timeout is delayed by a tick or
 610          * more.
 611          */
 612         if (update) {
 613                 /* SDC threads are not allowed to change cpupart bindings. */
 614                 ASSERT(t->t_cpupart == sdc->sdc_pset->sdp_cpupart);
 615 
 616                 /* If we were at MAXPRI, account for our onproc time. */
 617                 if (t->t_pri == sdc->sdc_maxpri &&
 618                     sdc->sdc_last_base_O != 0 &&
 619                     sdc->sdc_last_base_O < newO) {
 620                         sdc->sdc_last_O = newO - sdc->sdc_last_base_O;
 621                         sdc->sdc_pset->sdp_onproc_time +=
 622                             (uint64_t)sdc->sdc_last_O;
 623                         sdc->sdc_pset->sdp_onproc_threads++;
 624                 } else {
 625                         sdc->sdc_last_O = 0;
 626                 }
 627                 sdc->sdc_last_base_O = newO;
 628 
 629                 sdc->sdc_update_ticks = sdc->sdc_ticks + sysdc_update_ticks + 1;
 630                 return (1);
 631         }
 632 
 633         /*
 634          * Like sysdc_update(), sysdc_tick() always wants to update the
 635          * thread's priority, so that the CPU is surrendered if necessary.
 636          * We reset sdc_update_ticks so that if the timeout continues to be
 637          * delayed, we'll update at the regular interval.
 638          */
 639         if (tick) {
 640                 ASSERT(sdc->sdc_ticks == sdc->sdc_update_ticks);
 641                 sdc->sdc_update_ticks = sdc->sdc_ticks + sysdc_update_ticks;
 642                 return (1);
 643         }
 644 
 645         /*
 646          * Otherwise, only tell our callers to update the priority if it has
 647          * changed.
 648          */
 649         return (sdc->sdc_epri != t->t_pri);
 650 }
 651 
 652 static void
 653 sysdc_update_pri(sysdc_t *sdc, uint_t flags)
 654 {
 655         kthread_t *t = sdc->sdc_thread;
 656 
 657         ASSERT(THREAD_LOCK_HELD(t));
 658 
 659         if (sysdc_compute_pri(sdc, flags)) {
 660                 if (!thread_change_pri(t, sdc->sdc_epri, 0)) {
 661                         cpu_surrender(t);
 662                 }
 663         }
 664 }
 665 
 666 /*
 667  * Add a thread onto the active list.  It will only be removed by
 668  * sysdc_update().
 669  */
 670 static void
 671 sysdc_activate(sysdc_t *sdc)
 672 {
 673         sysdc_t *volatile *headp = &SYSDC_LIST(sdc)->sdl_list;
 674         sysdc_t         *head;
 675         kthread_t       *t = sdc->sdc_thread;
 676 
 677         SYSDC_INC_STAT(sysdc_activate_enter);
 678 
 679         ASSERT(sdc->sdc_next == NULL);
 680         ASSERT(THREAD_LOCK_HELD(t));
 681 
 682         do {
 683                 head = *headp;
 684                 sdc->sdc_next = head;
 685         } while (atomic_cas_ptr(headp, head, sdc) != head);
 686 }
 687 
 688 /*
 689  * sysdc_update() has two jobs:
 690  *
 691  *      1. It updates the priorities of all active SDC threads on the system.
 692  *      2. It measures pset CPU usage and enforces sysdc_max_pset_DC.
 693  */
 694 static void
 695 sysdc_update(void *arg)
 696 {
 697         int             idx;
 698         sysdc_t         *freelist = NULL;
 699         sysdc_pset_t    *cur;
 700         hrtime_t        now, diff;
 701         uint_t          redeploy = 1;
 702 
 703         SYSDC_INC_STAT(sysdc_update_enter);
 704 
 705         ASSERT(sysdc_update_timeout_started);
 706 
 707         /*
 708          * If this is our first time through, diff will be gigantic, and
 709          * no breaks will be necessary.
 710          */
 711         now = gethrtime();
 712         diff = now - sysdc_last_update;
 713         sysdc_last_update = now;
 714 
 715         mutex_enter(&sysdc_pset_lock);
 716         for (cur = list_head(&sysdc_psets); cur != NULL;
 717             cur = list_next(&sysdc_psets, cur)) {
 718                 boolean_t breaking = (cur->sdp_should_break != 0);
 719 
 720                 if (cur->sdp_need_break != breaking) {
 721                         DTRACE_PROBE2(sdc__pset__break, sysdc_pset_t *, cur,
 722                             boolean_t, breaking);
 723                 }
 724                 cur->sdp_onproc_time = 0;
 725                 cur->sdp_onproc_threads = 0;
 726                 cur->sdp_need_break = breaking;
 727         }
 728         mutex_exit(&sysdc_pset_lock);
 729 
 730         for (idx = 0; idx < SYSDC_NLISTS; idx++) {
 731                 sysdc_list_t            *sdl = &sysdc_active[idx];
 732                 sysdc_t *volatile       *headp = &sdl->sdl_list;
 733                 sysdc_t                 *head, *tail;
 734                 sysdc_t                 **prevptr;
 735 
 736                 if (*headp == &sysdc_dummy)
 737                         continue;
 738 
 739                 /* Prevent any threads from exiting while we're poking them. */
 740                 mutex_enter(&sdl->sdl_lock);
 741 
 742                 /*
 743                  * Each sdl_list contains a singly-linked list of active
 744                  * threads. Threads which become active while we are
 745                  * processing the list will be added to sdl_list.  Since we
 746                  * don't want that to interfere with our own processing, we
 747                  * swap in an empty list.  Any newly active threads will
 748                  * go on to this empty list.  When finished, we'll put any
 749                  * such threads at the end of the processed list.
 750                  */
 751                 head = atomic_swap_ptr(headp, &sysdc_dummy);
 752                 prevptr = &head;
 753                 while (*prevptr != &sysdc_dummy) {
 754                         sysdc_t         *const  sdc = *prevptr;
 755                         kthread_t       *const  t = sdc->sdc_thread;
 756 
 757                         /*
 758                          * If the thread has exited, move its sysdc_t onto
 759                          * freelist, to be freed later.
 760                          */
 761                         if (t == NULL) {
 762                                 *prevptr = sdc->sdc_next;
 763                                 SYSDC_INC_STAT(sysdc_update_exited);
 764                                 sdc->sdc_next = freelist;
 765                                 freelist = sdc;
 766                                 continue;
 767                         }
 768 
 769                         thread_lock(t);
 770                         if (t->t_cid != sysdccid) {
 771                                 thread_unlock(t);
 772                                 prevptr = &sdc->sdc_next;
 773                                 SYSDC_INC_STAT(sysdc_update_not_sdc);
 774                                 continue;
 775                         }
 776                         ASSERT(t->t_cldata == sdc);
 777 
 778                         /*
 779                          * If the thread has been sleeping for longer
 780                          * than sysdc_prune_interval, make it inactive by
 781                          * removing it from the list.
 782                          */
 783                         if (!(t->t_state & (TS_RUN | TS_ONPROC)) &&
 784                             sdc->sdc_sleep_updates != 0 &&
 785                             (sdc->sdc_sleep_updates - sdc->sdc_nupdates) >
 786                             sysdc_prune_updates) {
 787                                 *prevptr = sdc->sdc_next;
 788                                 SYSDC_INC_STAT(sysdc_update_idle);
 789                                 sdc->sdc_next = NULL;
 790                                 thread_unlock(t);
 791                                 continue;
 792                         }
 793                         sysdc_update_pri(sdc, SDC_UPDATE_TIMEOUT);
 794                         thread_unlock(t);
 795 
 796                         prevptr = &sdc->sdc_next;
 797                 }
 798 
 799                 /*
 800                  * Add our list to the bucket, putting any new entries
 801                  * added while we were working at the tail of the list.
 802                  */
 803                 do {
 804                         tail = *headp;
 805                         *prevptr = tail;
 806                 } while (atomic_cas_ptr(headp, tail, head) != tail);
 807 
 808                 mutex_exit(&sdl->sdl_lock);
 809         }
 810 
 811         mutex_enter(&sysdc_pset_lock);
 812         for (cur = list_head(&sysdc_psets); cur != NULL;
 813             cur = list_next(&sysdc_psets, cur)) {
 814 
 815                 cur->sdp_vtime_last_interval =
 816                     diff * cur->sdp_cpupart->cp_ncpus;
 817                 cur->sdp_DC_last_interval =
 818                     (cur->sdp_onproc_time * SYSDC_DC_MAX) /
 819                     cur->sdp_vtime_last_interval;
 820 
 821                 if (cur->sdp_should_break > 0) {
 822                         cur->sdp_should_break--;     /* breaking */
 823                         continue;
 824                 }
 825                 if (cur->sdp_dont_break > 0) {
 826                         cur->sdp_dont_break--;       /* waiting before checking */
 827                         continue;
 828                 }
 829                 if (cur->sdp_DC_last_interval > sysdc_max_pset_DC) {
 830                         cur->sdp_should_break = sysdc_break_updates;
 831                         cur->sdp_dont_break = sysdc_nobreak_updates;
 832                         SYSDC_INC_STAT(sysdc_update_take_break);
 833                 }
 834         }
 835 
 836         /*
 837          * If there are no sysdc_psets, there can be no threads, so
 838          * we can stop doing our timeout.  Since we're holding the
 839          * sysdc_pset_lock, no new sysdc_psets can come in, which will
 840          * prevent anyone from racing with this and dropping our timeout
 841          * on the floor.
 842          */
 843         if (list_is_empty(&sysdc_psets)) {
 844                 SYSDC_INC_STAT(sysdc_update_no_psets);
 845                 ASSERT(sysdc_update_timeout_started);
 846                 sysdc_update_timeout_started = 0;
 847 
 848                 redeploy = 0;
 849         }
 850         mutex_exit(&sysdc_pset_lock);
 851 
 852         while (freelist != NULL) {
 853                 sysdc_t *cur = freelist;
 854                 freelist = cur->sdc_next;
 855                 kmem_free(cur, sizeof (*cur));
 856         }
 857 
 858         if (redeploy) {
 859                 (void) timeout(sysdc_update, arg, sysdc_update_ticks);
 860         }
 861 }
 862 
 863 static void
 864 sysdc_preempt(kthread_t *t)
 865 {
 866         ASSERT(t == curthread);
 867         ASSERT(THREAD_LOCK_HELD(t));
 868 
 869         setbackdq(t);           /* give others a chance to run */
 870 }
 871 
 872 static void
 873 sysdc_tick(kthread_t *t)
 874 {
 875         sysdc_t *sdc;
 876 
 877         thread_lock(t);
 878         if (t->t_cid != sysdccid) {
 879                 SYSDC_INC_STAT(sysdc_tick_not_sdc);
 880                 thread_unlock(t);
 881                 return;
 882         }
 883         sdc = t->t_cldata;
 884         if (t->t_state == TS_ONPROC &&
 885             t->t_pri < t->t_disp_queue->disp_maxrunpri) {
 886                 cpu_surrender(t);
 887         }
 888 
 889         if (t->t_state == TS_ONPROC || t->t_state == TS_RUN) {
 890                 ASSERT(sdc->sdc_sleep_updates == 0);
 891         }
 892 
 893         ASSERT(sdc->sdc_ticks != sdc->sdc_update_ticks);
 894         sdc->sdc_ticks++;
 895         if (sdc->sdc_ticks == sdc->sdc_update_ticks) {
 896                 SYSDC_INC_STAT(sysdc_tick_quantum_expired);
 897                 sysdc_update_pri(sdc, SDC_UPDATE_TICK);
 898                 ASSERT(sdc->sdc_ticks != sdc->sdc_update_ticks);
 899         }
 900         thread_unlock(t);
 901 }
 902 
 903 static void
 904 sysdc_setrun(kthread_t *t)
 905 {
 906         sysdc_t *sdc = t->t_cldata;
 907 
 908         ASSERT(THREAD_LOCK_HELD(t));    /* t should be in transition */
 909 
 910         sdc->sdc_sleep_updates = 0;
 911 
 912         if (sdc->sdc_next == NULL) {
 913                 /*
 914                  * Since we're in transition, we don't want to use the
 915                  * full thread_update_pri().
 916                  */
 917                 if (sysdc_compute_pri(sdc, 0)) {
 918                         THREAD_CHANGE_PRI(t, sdc->sdc_epri);
 919                 }
 920                 sysdc_activate(sdc);
 921 
 922                 ASSERT(sdc->sdc_next != NULL);
 923         }
 924 
 925         setbackdq(t);
 926 }
 927 
 928 static void
 929 sysdc_wakeup(kthread_t *t)
 930 {
 931         sysdc_setrun(t);
 932 }
 933 
 934 static void
 935 sysdc_sleep(kthread_t *t)
 936 {
 937         sysdc_t *sdc = t->t_cldata;
 938 
 939         ASSERT(THREAD_LOCK_HELD(t));    /* t should be in transition */
 940 
 941         sdc->sdc_sleep_updates = sdc->sdc_nupdates;
 942 }
 943 
 944 /*ARGSUSED*/
 945 static int
 946 sysdc_enterclass(kthread_t *t, id_t cid, void *parmsp, cred_t *reqpcredp,
 947     void *bufp)
 948 {
 949         cpupart_t *const cpupart = t->t_cpupart;
 950         sysdc_t *sdc = bufp;
 951         sysdc_params_t *sdpp = parmsp;
 952         sysdc_pset_t *newpset = sdc->sdc_pset;
 953         sysdc_pset_t *pset;
 954         int start_timeout;
 955 
 956         if (t->t_cid != syscid)
 957                 return (EPERM);
 958 
 959         ASSERT(ttolwp(t) != NULL);
 960         ASSERT(sdpp != NULL);
 961         ASSERT(newpset != NULL);
 962         ASSERT(sysdc_param_init);
 963 
 964         ASSERT(sdpp->sdp_minpri >= sysdc_minpri);
 965         ASSERT(sdpp->sdp_maxpri <= sysdc_maxpri);
 966         ASSERT(sdpp->sdp_DC >= sysdc_minDC);
 967         ASSERT(sdpp->sdp_DC <= sysdc_maxDC);
 968 
 969         sdc->sdc_thread = t;
 970         sdc->sdc_pri = sdpp->sdp_maxpri;  /* start off maximally */
 971         sdc->sdc_minpri = sdpp->sdp_minpri;
 972         sdc->sdc_maxpri = sdpp->sdp_maxpri;
 973         sdc->sdc_target_DC = sdpp->sdp_DC;
 974         sdc->sdc_ticks = 0;
 975         sdc->sdc_update_ticks = sysdc_update_ticks + 1;
 976 
 977         /* Assign ourselves to the appropriate pset. */
 978         sdc->sdc_pset = NULL;
 979         mutex_enter(&sysdc_pset_lock);
 980         for (pset = list_head(&sysdc_psets); pset != NULL;
 981             pset = list_next(&sysdc_psets, pset)) {
 982                 if (pset->sdp_cpupart == cpupart) {
 983                         break;
 984                 }
 985         }
 986         if (pset == NULL) {
 987                 pset = newpset;
 988                 newpset = NULL;
 989                 pset->sdp_cpupart = cpupart;
 990                 list_insert_tail(&sysdc_psets, pset);
 991         }
 992         pset->sdp_nthreads++;
 993         ASSERT(pset->sdp_nthreads > 0);
 994 
 995         sdc->sdc_pset = pset;
 996 
 997         start_timeout = (sysdc_update_timeout_started == 0);
 998         sysdc_update_timeout_started = 1;
 999         mutex_exit(&sysdc_pset_lock);
1000 
1001         if (newpset != NULL)
1002                 kmem_free(newpset, sizeof (*newpset));
1003 
1004         /* Update t's scheduling class and priority. */
1005         thread_lock(t);
1006         t->t_clfuncs = &(sclass[cid].cl_funcs->thread);
1007         t->t_cid = cid;
1008         t->t_cldata = sdc;
1009         t->t_schedflag |= TS_RUNQMATCH;
1010 
1011         sysdc_update_pri(sdc, SDC_UPDATE_INITIAL);
1012         thread_unlock(t);
1013 
1014         /* Kick off the thread timeout if we're the first one in. */
1015         if (start_timeout) {
1016                 (void) timeout(sysdc_update, NULL, sysdc_update_ticks);
1017         }
1018 
1019         return (0);
1020 }
1021 
1022 static void
1023 sysdc_leave(sysdc_t *sdc)
1024 {
1025         sysdc_pset_t *sdp = sdc->sdc_pset;
1026         sysdc_list_t *sdl = SYSDC_LIST(sdc);
1027         uint_t freedc;
1028 
1029         mutex_enter(&sdl->sdl_lock);             /* block sysdc_update() */
1030         sdc->sdc_thread = NULL;
1031         freedc = (sdc->sdc_next == NULL);
1032         mutex_exit(&sdl->sdl_lock);
1033 
1034         mutex_enter(&sysdc_pset_lock);
1035         ASSERT(sdp != NULL);
1036         ASSERT(sdp->sdp_nthreads > 0);
1037         --sdp->sdp_nthreads;
1038         if (sdp->sdp_nthreads == 0) {
1039                 list_remove(&sysdc_psets, sdp);
1040         } else {
1041                 sdp = NULL;
1042         }
1043         mutex_exit(&sysdc_pset_lock);
1044 
1045         if (freedc)
1046                 kmem_free(sdc, sizeof (*sdc));
1047         if (sdp != NULL)
1048                 kmem_free(sdp, sizeof (*sdp));
1049 }
1050 
1051 static void
1052 sysdc_exitclass(void *buf)
1053 {
1054         sysdc_leave((sysdc_t *)buf);
1055 }
1056 
1057 /*ARGSUSED*/
1058 static int
1059 sysdc_canexit(kthread_t *t, cred_t *reqpcredp)
1060 {
1061         /* Threads cannot exit SDC once joined, except in a body bag. */
1062         return (EPERM);
1063 }
1064 
1065 static void
1066 sysdc_exit(kthread_t *t)
1067 {
1068         sysdc_t *sdc;
1069 
1070         /* We're exiting, so we just rejoin the SYS class. */
1071         thread_lock(t);
1072         ASSERT(t->t_cid == sysdccid);
1073         sdc = t->t_cldata;
1074         t->t_cid = syscid;
1075         t->t_cldata = NULL;
1076         t->t_clfuncs = &(sclass[syscid].cl_funcs->thread);
1077         (void) thread_change_pri(t, maxclsyspri, 0);
1078         t->t_schedflag &= ~TS_RUNQMATCH;
1079         thread_unlock_nopreempt(t);
1080 
1081         /* Unlink the sdc from everything. */
1082         sysdc_leave(sdc);
1083 }
1084 
1085 /*ARGSUSED*/
1086 static int
1087 sysdc_fork(kthread_t *t, kthread_t *ct, void *bufp)
1088 {
1089         /*
1090          * Threads cannot be created with SDC as their class; they must
1091          * be created as SYS and then added with sysdc_thread_enter().
1092          * Because of this restriction, sysdc_fork() should never be called.
1093          */
1094         panic("sysdc cannot be forked");
1095 
1096         return (ENOSYS);
1097 }
1098 
1099 /*ARGSUSED*/
1100 static void
1101 sysdc_forkret(kthread_t *t, kthread_t *ct)
1102 {
1103         /* SDC threads are part of system processes, which never fork. */
1104         panic("sysdc cannot be forked");
1105 }
1106 
1107 static pri_t
1108 sysdc_globpri(kthread_t *t)
1109 {
1110         return (t->t_epri);
1111 }
1112 
1113 /*ARGSUSED*/
1114 static pri_t
1115 sysdc_no_swap(kthread_t *t, int flags)
1116 {
1117         /* SDC threads cannot be swapped. */
1118         return (-1);
1119 }
1120 
1121 /*
1122  * Get maximum and minimum priorities enjoyed by SDC threads.
1123  */
1124 static int
1125 sysdc_getclpri(pcpri_t *pcprip)
1126 {
1127         pcprip->pc_clpmax = sysdc_maxpri;
1128         pcprip->pc_clpmin = sysdc_minpri;
1129         return (0);
1130 }
1131 
1132 /*ARGSUSED*/
1133 static int
1134 sysdc_getclinfo(void *arg)
1135 {
1136         return (0);             /* no class-specific info */
1137 }
1138 
1139 /*ARGSUSED*/
1140 static int
1141 sysdc_alloc(void **p, int flag)
1142 {
1143         sysdc_t *new;
1144 
1145         *p = NULL;
1146         if ((new = kmem_zalloc(sizeof (*new), flag)) == NULL) {
1147                 return (ENOMEM);
1148         }
1149         if ((new->sdc_pset = kmem_zalloc(sizeof (*new->sdc_pset), flag)) ==
1150             NULL) {
1151                 kmem_free(new, sizeof (*new));
1152                 return (ENOMEM);
1153         }
1154         *p = new;
1155         return (0);
1156 }
1157 
1158 static void
1159 sysdc_free(void *p)
1160 {
1161         sysdc_t *sdc = p;
1162 
1163         if (sdc != NULL) {
1164                 /*
1165                  * We must have failed CL_ENTERCLASS(), so our pset should be
1166                  * there and unused.
1167                  */
1168                 ASSERT(sdc->sdc_pset != NULL);
1169                 ASSERT(sdc->sdc_pset->sdp_cpupart == NULL);
1170                 kmem_free(sdc->sdc_pset, sizeof (*sdc->sdc_pset));
1171                 kmem_free(sdc, sizeof (*sdc));
1172         }
1173 }
1174 
1175 static int sysdc_enosys();      /* Boy, ANSI-C's K&R compatibility is weird. */
1176 static int sysdc_einval();
1177 static void sysdc_nullsys();
1178 
1179 static struct classfuncs sysdc_classfuncs = {
1180         /* messages to class manager */
1181         {
1182                 sysdc_enosys,   /* admin */
1183                 sysdc_getclinfo,
1184                 sysdc_enosys,   /* parmsin */
1185                 sysdc_enosys,   /* parmsout */
1186                 sysdc_enosys,   /* vaparmsin */
1187                 sysdc_enosys,   /* vaparmsout */
1188                 sysdc_getclpri,
1189                 sysdc_alloc,
1190                 sysdc_free,
1191         },
1192         /* operations on threads */
1193         {
1194                 sysdc_enterclass,
1195                 sysdc_exitclass,
1196                 sysdc_canexit,
1197                 sysdc_fork,
1198                 sysdc_forkret,
1199                 sysdc_nullsys,  /* parmsget */
1200                 sysdc_enosys,   /* parmsset */
1201                 sysdc_nullsys,  /* stop */
1202                 sysdc_exit,
1203                 sysdc_nullsys,  /* active */
1204                 sysdc_nullsys,  /* inactive */
1205                 sysdc_no_swap,  /* swapin */
1206                 sysdc_no_swap,  /* swapout */
1207                 sysdc_nullsys,  /* trapret */
1208                 sysdc_preempt,
1209                 sysdc_setrun,
1210                 sysdc_sleep,
1211                 sysdc_tick,
1212                 sysdc_wakeup,
1213                 sysdc_einval,   /* donice */
1214                 sysdc_globpri,
1215                 sysdc_nullsys,  /* set_process_group */
1216                 sysdc_nullsys,  /* yield */
1217                 sysdc_einval,   /* doprio */
1218         }
1219 };
1220 
1221 static int
1222 sysdc_enosys()
1223 {
1224         return (ENOSYS);
1225 }
1226 
1227 static int
1228 sysdc_einval()
1229 {
1230         return (EINVAL);
1231 }
1232 
1233 static void
1234 sysdc_nullsys()
1235 {
1236 }
1237 
1238 /*ARGSUSED*/
1239 static pri_t
1240 sysdc_init(id_t cid, int clparmsz, classfuncs_t **clfuncspp)
1241 {
1242         int idx;
1243 
1244         list_create(&sysdc_psets, sizeof (sysdc_pset_t),
1245             offsetof(sysdc_pset_t, sdp_node));
1246 
1247         for (idx = 0; idx < SYSDC_NLISTS; idx++) {
1248                 sysdc_active[idx].sdl_list = &sysdc_dummy;
1249         }
1250 
1251         sysdc_initparam();
1252 
1253         sysdccid = cid;
1254         *clfuncspp = &sysdc_classfuncs;
1255 
1256         return ((pri_t)v.v_maxsyspri);
1257 }
1258 
1259 static struct sclass csw = {
1260         "SDC",
1261         sysdc_init,
1262         0
1263 };
1264 
1265 static struct modlsched modlsched = {
1266         &mod_schedops, "system duty cycle scheduling class", &csw
1267 };
1268 
1269 static struct modlinkage modlinkage = {
1270         MODREV_1, { (void *)&modlsched, NULL }
1271 };
1272 
1273 int
1274 _init()
1275 {
1276         return (mod_install(&modlinkage));
1277 }
1278 
1279 int
1280 _fini()
1281 {
1282         return (EBUSY);         /* can't unload for now */
1283 }
1284 
1285 int
1286 _info(struct modinfo *modinfop)
1287 {
1288         return (mod_info(&modlinkage, modinfop));
1289 }
1290 
1291 /* --- consolidation-private interfaces --- */
1292 void
1293 sysdc_thread_enter(kthread_t *t, uint_t dc, uint_t flags)
1294 {
1295         void *buf = NULL;
1296         sysdc_params_t sdp;
1297 
1298         SYSDC_INC_STAT(sysdc_thread_enter_enter);
1299 
1300         ASSERT(sysdc_param_init);
1301         ASSERT(sysdccid >= 0);
1302 
1303         ASSERT((flags & ~SYSDC_THREAD_BATCH) == 0);
1304 
1305         sdp.sdp_minpri = sysdc_minpri;
1306         sdp.sdp_maxpri = sysdc_maxpri;
1307         sdp.sdp_DC = MAX(MIN(dc, sysdc_maxDC), sysdc_minDC);
1308 
1309         VERIFY0(CL_ALLOC(&buf, sysdccid, KM_SLEEP));
1310 
1311         ASSERT(t->t_lwp != NULL);
1312         ASSERT(t->t_cid == syscid);
1313         ASSERT(t->t_cldata == NULL);
1314         VERIFY0(CL_CANEXIT(t, NULL));
1315         VERIFY0(CL_ENTERCLASS(t, sysdccid, &sdp, kcred, buf));
1316         CL_EXITCLASS(syscid, NULL);
1317 }