Mercurial > illumos > illumos-gate

changeset 2918:5e0808c08daa

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
6478928 buffer recycling causes long arc mutex spins
author maybee
date Fri, 13 Oct 2006 14:02:05 -0700
parents 27816039d166
children f56e9aa9c109
files usr/src/uts/common/fs/zfs/arc.c
diffstat 1 files changed, 14 insertions(+), 11 deletions(-) [+]
line wrap: on
line diff
--- a/usr/src/uts/common/fs/zfs/arc.c	Fri Oct 13 12:08:49 2006 -0700
+++ b/usr/src/uts/common/fs/zfs/arc.c	Fri Oct 13 14:02:05 2006 -0700
@@ -934,10 +934,10 @@
 {
 	arc_state_t *evicted_state;
 	uint64_t bytes_evicted = 0, skipped = 0, missed = 0;
-	arc_buf_hdr_t *ab, *ab_prev;
+	arc_buf_hdr_t *ab, *ab_prev = NULL;
 	kmutex_t *hash_lock;
 	boolean_t have_lock;
-	void *steal = NULL;
+	void *stolen = NULL;
 
 	ASSERT(state == arc.mru || state == arc.mfu);
 
@@ -955,7 +955,9 @@
 			skipped++;
 			continue;
 		}
-		if (recycle && (ab->b_size != bytes || ab->b_datacnt > 1))
+		/* "lookahead" for better eviction candidate */
+		if (recycle && ab->b_size != bytes &&
+		    ab_prev && ab_prev->b_size == bytes)
 			continue;
 		hash_lock = HDR_LOCK(ab);
 		have_lock = MUTEX_HELD(hash_lock);
@@ -966,19 +968,23 @@
 				arc_buf_t *buf = ab->b_buf;
 				if (buf->b_data) {
 					bytes_evicted += ab->b_size;
-					if (recycle)
-						steal = buf->b_data;
+					if (recycle && ab->b_size == bytes) {
+						stolen = buf->b_data;
+						recycle = FALSE;
+					}
 				}
 				if (buf->b_efunc) {
 					mutex_enter(&arc_eviction_mtx);
-					arc_buf_destroy(buf, recycle, FALSE);
+					arc_buf_destroy(buf,
+					    buf->b_data == stolen, FALSE);
 					ab->b_buf = buf->b_next;
 					buf->b_hdr = &arc_eviction_hdr;
 					buf->b_next = arc_eviction_list;
 					arc_eviction_list = buf;
 					mutex_exit(&arc_eviction_mtx);
 				} else {
-					arc_buf_destroy(buf, recycle, TRUE);
+					arc_buf_destroy(buf,
+					    buf->b_data == stolen, TRUE);
 				}
 			}
 			ASSERT(ab->b_datacnt == 0);
@@ -1005,7 +1011,7 @@
 		atomic_add_64(&arc.evict_skip, skipped);
 	if (missed)
 		atomic_add_64(&arc.mutex_miss, missed);
-	return (steal);
+	return (stolen);
 }
 
 /*
@@ -1470,12 +1476,9 @@
 		state =  (mfu_space > arc.mfu->size) ? arc.mru : arc.mfu;
 	}
 	if ((buf->b_data = arc_evict(state, size, TRUE)) == NULL) {
-		(void) arc_evict(state, size, FALSE);
 		buf->b_data = zio_buf_alloc(size);
 		atomic_add_64(&arc.size, size);
 		atomic_add_64(&arc.recycle_miss, 1);
-		if (arc.size > arc.c)
-			arc_adjust();
 	}
 	ASSERT(buf->b_data != NULL);
 out: