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Date:      Sat, 13 Mar 2010 21:41:53 +0000 (UTC)
From:      Kip Macy <kmacy@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r205132 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs
Message-ID:  <201003132141.o2DLfroC041203@svn.freebsd.org>
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Author: kmacy
Date: Sat Mar 13 21:41:52 2010
New Revision: 205132
URL: http://svn.freebsd.org/changeset/base/205132

Log:
  Don't bottleneck on acquiring the stream locks - this avoids a massive
  drop off in throughput with large numbers of simultaneous reads
  
  MFC after:	7 days

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c	Sat Mar 13 21:28:14 2010	(r205131)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dmu_zfetch.c	Sat Mar 13 21:41:52 2010	(r205132)
@@ -49,11 +49,11 @@ uint32_t	zfetch_block_cap = 256;
 uint64_t	zfetch_array_rd_sz = 1024 * 1024;
 
 SYSCTL_DECL(_vfs_zfs);
-SYSCTL_INT(_vfs_zfs, OID_AUTO, prefetch_disable, CTLFLAG_RDTUN,
+SYSCTL_INT(_vfs_zfs, OID_AUTO, prefetch_disable, CTLFLAG_RW,
     &zfs_prefetch_disable, 0, "Disable prefetch");
 SYSCTL_NODE(_vfs_zfs, OID_AUTO, zfetch, CTLFLAG_RW, 0, "ZFS ZFETCH");
 TUNABLE_INT("vfs.zfs.zfetch.max_streams", &zfetch_max_streams);
-SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_streams, CTLFLAG_RDTUN,
+SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, max_streams, CTLFLAG_RW,
     &zfetch_max_streams, 0, "Max # of streams per zfetch");
 TUNABLE_INT("vfs.zfs.zfetch.min_sec_reap", &zfetch_min_sec_reap);
 SYSCTL_UINT(_vfs_zfs_zfetch, OID_AUTO, min_sec_reap, CTLFLAG_RDTUN,
@@ -338,8 +338,10 @@ top:
 
 			reset = !prefetched && zs->zst_len > 1;
 
-			mutex_enter(&zs->zst_lock);
-
+			if (mutex_tryenter(&zs->zst_lock) == 0) {
+				rc = 1;
+				goto out;
+			}
 			if (zh->zst_offset != zs->zst_offset + zs->zst_len) {
 				mutex_exit(&zs->zst_lock);
 				goto top;
@@ -363,8 +365,10 @@ top:
 
 			reset = !prefetched && zs->zst_len > 1;
 
-			mutex_enter(&zs->zst_lock);
-
+			if (mutex_tryenter(&zs->zst_lock) == 0) {
+				rc = 1;
+				goto out;
+			}
 			if (zh->zst_offset != zs->zst_offset - zh->zst_len) {
 				mutex_exit(&zs->zst_lock);
 				goto top;
@@ -391,8 +395,10 @@ top:
 		    zs->zst_len) && (zs->zst_len != zs->zst_stride)) {
 			/* strided forward access */
 
-			mutex_enter(&zs->zst_lock);
-
+			if (mutex_tryenter(&zs->zst_lock) == 0) {
+				rc = 1;
+				goto out;
+			}
 			if ((zh->zst_offset - zs->zst_offset - zs->zst_stride >=
 			    zs->zst_len) || (zs->zst_len == zs->zst_stride)) {
 				mutex_exit(&zs->zst_lock);
@@ -408,8 +414,10 @@ top:
 		    zs->zst_len) && (zs->zst_len != zs->zst_stride)) {
 			/* strided reverse access */
 
-			mutex_enter(&zs->zst_lock);
-
+			if (mutex_tryenter(&zs->zst_lock) == 0) {
+				rc = 1;
+				goto out;
+			}
 			if ((zh->zst_offset - zs->zst_offset + zs->zst_stride >=
 			    zs->zst_len) || (zs->zst_len == zs->zst_stride)) {
 				mutex_exit(&zs->zst_lock);

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