From owner-svn-src-vendor@freebsd.org Mon Jan 22 05:55:44 2018 Return-Path: Delivered-To: svn-src-vendor@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id C9CD9ED03BD; Mon, 22 Jan 2018 05:55:44 +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 A2E766CA94; Mon, 22 Jan 2018 05:55:44 +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 B47B7163E2; Mon, 22 Jan 2018 05:55:43 +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 w0M5thh8062501; Mon, 22 Jan 2018 05:55:43 GMT (envelope-from mav@FreeBSD.org) Received: (from mav@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w0M5th55062500; Mon, 22 Jan 2018 05:55:43 GMT (envelope-from mav@FreeBSD.org) Message-Id: <201801220555.w0M5th55062500@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mav set sender to mav@FreeBSD.org using -f From: Alexander Motin Date: Mon, 22 Jan 2018 05:55:43 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-vendor@freebsd.org Subject: svn commit: r328253 - vendor-sys/illumos/dist/uts/common/fs/zfs X-SVN-Group: vendor-sys X-SVN-Commit-Author: mav X-SVN-Commit-Paths: vendor-sys/illumos/dist/uts/common/fs/zfs X-SVN-Commit-Revision: 328253 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-vendor@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the vendor work area tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 22 Jan 2018 05:55:44 -0000 Author: mav Date: Mon Jan 22 05:55:43 2018 New Revision: 328253 URL: https://svnweb.freebsd.org/changeset/base/328253 Log: 8835 Speculative prefetch in ZFS not working for misaligned reads illumos/illumos-gate@5cb8d943bc8513c6230589aad5a409d58b0297cb https://www.illumos.org/issues/8835: Sequential reads not aligned to block size are not detected by ZFS prefetcher as sequential, killing prefetch and severely hurting performance. It is caused by dmu_zfetch() in case of misaligned sequential accesses being called with overlap of one block. Reviewed by: Matthew Ahrens Reviewed by: Allan Jude Approved by: Gordon Ross Author: Alexander Motin Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_zfetch.c Modified: vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_zfetch.c ============================================================================== --- vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_zfetch.c Mon Jan 22 05:52:39 2018 (r328252) +++ vendor-sys/illumos/dist/uts/common/fs/zfs/dmu_zfetch.c Mon Jan 22 05:55:43 2018 (r328253) @@ -224,19 +224,33 @@ dmu_zfetch(zfetch_t *zf, uint64_t blkid, uint64_t nblk rw_enter(&zf->zf_rwlock, RW_READER); + /* + * Find matching prefetch stream. Depending on whether the accesses + * are block-aligned, first block of the new access may either follow + * the last block of the previous access, or be equal to it. + */ for (zs = list_head(&zf->zf_stream); zs != NULL; zs = list_next(&zf->zf_stream, zs)) { - if (blkid == zs->zs_blkid) { + if (blkid == zs->zs_blkid || blkid + 1 == zs->zs_blkid) { mutex_enter(&zs->zs_lock); /* * zs_blkid could have changed before we * acquired zs_lock; re-check them here. */ - if (blkid != zs->zs_blkid) { - mutex_exit(&zs->zs_lock); - continue; + if (blkid == zs->zs_blkid) { + break; + } else if (blkid + 1 == zs->zs_blkid) { + blkid++; + nblks--; + if (nblks == 0) { + /* Already prefetched this before. */ + mutex_exit(&zs->zs_lock); + rw_exit(&zf->zf_rwlock); + return; + } + break; } - break; + mutex_exit(&zs->zs_lock); } }