4045 zfs write throttle & i/o scheduler performance work
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>

*** 21,31 ****
  /*
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  /*
!  * Copyright (c) 2012 by Delphix. All rights reserved.
   */
  
  #ifndef _SYS_TXG_H
  #define _SYS_TXG_H
  
--- 21,31 ----
  /*
   * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  /*
!  * Copyright (c) 2013 by Delphix. All rights reserved.
   */
  
  #ifndef _SYS_TXG_H
  #define _SYS_TXG_H
  
*** 74,83 ****
--- 74,84 ----
  extern void txg_rele_to_sync(txg_handle_t *txghp);
  extern void txg_register_callbacks(txg_handle_t *txghp, list_t *tx_callbacks);
  
  extern void txg_delay(struct dsl_pool *dp, uint64_t txg, hrtime_t delta,
      hrtime_t resolution);
+ extern void txg_kick(struct dsl_pool *dp);
  
  /*
   * Wait until the given transaction group has finished syncing.
   * Try to make this happen as soon as possible (eg. kick off any
   * necessary syncs immediately).  If txg==0, wait for the currently open