Print this page
3741 zfs needs better comments
Submitted by: Will Andrews <willa@spectralogic.com>
Submitted by: Justin Gibbs <justing@spectralogic.com>
Submitted by: Alan Somers <alans@spectralogic.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
@@ -252,11 +252,22 @@
kstat_named_t arcstat_mru_ghost_hits;
kstat_named_t arcstat_mfu_hits;
kstat_named_t arcstat_mfu_ghost_hits;
kstat_named_t arcstat_deleted;
kstat_named_t arcstat_recycle_miss;
+ /*
+ * Number of buffers that could not be evicted because the hash lock
+ * was held by another thread. The lock may not necessarily be held
+ * by something using the same buffer, since hash locks are shared
+ * by multiple buffers.
+ */
kstat_named_t arcstat_mutex_miss;
+ /*
+ * Number of buffers skipped because they have I/O in progress, are
+ * indrect prefetch buffers that have not lived long enough, or are
+ * not from the spa we're trying to evict from.
+ */
kstat_named_t arcstat_evict_skip;
kstat_named_t arcstat_evict_l2_cached;
kstat_named_t arcstat_evict_l2_eligible;
kstat_named_t arcstat_evict_l2_ineligible;
kstat_named_t arcstat_hash_elements;
@@ -2951,10 +2962,14 @@
vd = NULL;
}
mutex_exit(hash_lock);
+ /*
+ * At this point, we have a level 1 cache miss. Try again in
+ * L2ARC if possible.
+ */
ASSERT3U(hdr->b_size, ==, size);
DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
uint64_t, size, zbookmark_t *, zb);
ARCSTAT_BUMP(arcstat_misses);
ARCSTAT_CONDSTAT(!(hdr->b_flags & ARC_PREFETCH),
@@ -3141,12 +3156,12 @@
kmem_cache_free(buf_cache, buf);
return (1);
}
/*
- * Release this buffer from the cache. This must be done
- * after a read and prior to modifying the buffer contents.
+ * Release this buffer from the cache, making it an anonymous buffer. This
+ * must be done after a read and prior to modifying the buffer contents.
* If the buffer has more than one reference, we must make
* a new hdr for the buffer.
*/
void
arc_release(arc_buf_t *buf, void *tag)