From owner-svn-src-stable@freebsd.org Thu Apr 19 17:55:50 2018 Return-Path: Delivered-To: svn-src-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id DFE25F911F7; Thu, 19 Apr 2018 17:55:49 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 93B576FC28; Thu, 19 Apr 2018 17:55:49 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 8EA8A51FE; Thu, 19 Apr 2018 17:55:49 +0000 (UTC) (envelope-from mav@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id w3JHtnwP038974; Thu, 19 Apr 2018 17:55:49 GMT (envelope-from mav@FreeBSD.org) Received: (from mav@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w3JHtnAg038971; Thu, 19 Apr 2018 17:55:49 GMT (envelope-from mav@FreeBSD.org) Message-Id: <201804191755.w3JHtnAg038971@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mav set sender to mav@FreeBSD.org using -f From: Alexander Motin Date: Thu, 19 Apr 2018 17:55:49 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r332785 - in stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys X-SVN-Group: stable-11 X-SVN-Commit-Author: mav X-SVN-Commit-Paths: in stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs: . sys X-SVN-Commit-Revision: 332785 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-stable@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for all the -stable branches of the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Apr 2018 17:55:50 -0000 Author: mav Date: Thu Apr 19 17:55:48 2018 New Revision: 332785 URL: https://svnweb.freebsd.org/changeset/base/332785 Log: MFC r332523: 9433 Fix ARC hit rate When the compressed ARC feature was added in commit d3c2ae1 the method of reference counting in the ARC was modified. As part of this accounting change the arc_buf_add_ref() function was removed entirely. This would have be fine but the arc_buf_add_ref() function served a second undocumented purpose of updating the ARC access information when taking a hold on a dbuf. Without this logic in place a cached dbuf would not migrate its associated arc_buf_hdr_t to the MFU list. This would negatively impact the ARC hit rate, particularly on systems with a small ARC. This change reinstates the missing call to arc_access() from dbuf_hold() by implementing a new arc_buf_access() function. Reviewed-by: Giuseppe Di Natale Reviewed-by: Tony Hutter Reviewed-by: Tim Chase Reviewed by: George Wilson Reviewed-by: George Melikov Signed-off-by: Brian Behlendorf Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/arc.h Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c ============================================================================== --- stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Thu Apr 19 17:19:12 2018 (r332784) +++ stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c Thu Apr 19 17:55:48 2018 (r332785) @@ -540,8 +540,13 @@ typedef struct arc_stats { */ kstat_named_t arcstat_mutex_miss; /* + * Number of buffers skipped when updating the access state due to the + * header having already been released after acquiring the hash lock. + */ + kstat_named_t arcstat_access_skip; + /* * Number of buffers skipped because they have I/O in progress, are - * indrect prefetch buffers that have not lived long enough, or are + * indirect 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; @@ -796,6 +801,7 @@ static arc_stats_t arc_stats = { { "allocated", KSTAT_DATA_UINT64 }, { "deleted", KSTAT_DATA_UINT64 }, { "mutex_miss", KSTAT_DATA_UINT64 }, + { "access_skip", KSTAT_DATA_UINT64 }, { "evict_skip", KSTAT_DATA_UINT64 }, { "evict_not_enough", KSTAT_DATA_UINT64 }, { "evict_l2_cached", KSTAT_DATA_UINT64 }, @@ -5082,6 +5088,51 @@ arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock) } else { ASSERT(!"invalid arc state"); } +} + +/* + * This routine is called by dbuf_hold() to update the arc_access() state + * which otherwise would be skipped for entries in the dbuf cache. + */ +void +arc_buf_access(arc_buf_t *buf) +{ + mutex_enter(&buf->b_evict_lock); + arc_buf_hdr_t *hdr = buf->b_hdr; + + /* + * Avoid taking the hash_lock when possible as an optimization. + * The header must be checked again under the hash_lock in order + * to handle the case where it is concurrently being released. + */ + if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { + mutex_exit(&buf->b_evict_lock); + ARCSTAT_BUMP(arcstat_access_skip); + return; + } + + kmutex_t *hash_lock = HDR_LOCK(hdr); + mutex_enter(hash_lock); + + if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) { + mutex_exit(hash_lock); + mutex_exit(&buf->b_evict_lock); + ARCSTAT_BUMP(arcstat_access_skip); + return; + } + + mutex_exit(&buf->b_evict_lock); + + ASSERT(hdr->b_l1hdr.b_state == arc_mru || + hdr->b_l1hdr.b_state == arc_mfu); + + DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr); + arc_access(hdr, hash_lock); + mutex_exit(hash_lock); + + ARCSTAT_BUMP(arcstat_hits); + ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr), + demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits); } /* a generic arc_done_func_t which you can use */ Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c ============================================================================== --- stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Thu Apr 19 17:19:12 2018 (r332784) +++ stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c Thu Apr 19 17:55:48 2018 (r332785) @@ -2579,8 +2579,10 @@ top: return (SET_ERROR(ENOENT)); } - if (db->db_buf != NULL) + if (db->db_buf != NULL) { + arc_buf_access(db->db_buf); ASSERT3P(db->db.db_data, ==, db->db_buf->b_data); + } ASSERT(db->db_buf == NULL || arc_referenced(db->db_buf)); Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/arc.h ============================================================================== --- stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/arc.h Thu Apr 19 17:19:12 2018 (r332784) +++ stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/arc.h Thu Apr 19 17:55:48 2018 (r332785) @@ -169,6 +169,7 @@ void arc_loan_inuse_buf(arc_buf_t *buf, void *tag); void arc_buf_destroy(arc_buf_t *buf, void *tag); int arc_buf_size(arc_buf_t *buf); int arc_buf_lsize(arc_buf_t *buf); +void arc_buf_access(arc_buf_t *buf); void arc_release(arc_buf_t *buf, void *tag); int arc_released(arc_buf_t *buf); void arc_buf_freeze(arc_buf_t *buf);