From owner-svn-src-stable@freebsd.org Thu Mar 14 00:58:40 2019 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 BE8D61546A28; Thu, 14 Mar 2019 00:58:40 +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 TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 58F0980539; Thu, 14 Mar 2019 00:58:40 +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 1B3901A8E4; Thu, 14 Mar 2019 00:58:40 +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 x2E0wdVn082711; Thu, 14 Mar 2019 00:58:39 GMT (envelope-from mav@FreeBSD.org) Received: (from mav@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id x2E0wdqD082710; Thu, 14 Mar 2019 00:58:39 GMT (envelope-from mav@FreeBSD.org) Message-Id: <201903140058.x2E0wdqD082710@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mav set sender to mav@FreeBSD.org using -f From: Alexander Motin Date: Thu, 14 Mar 2019 00:58:39 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r345122 - stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs X-SVN-Group: stable-12 X-SVN-Commit-Author: mav X-SVN-Commit-Paths: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs X-SVN-Commit-Revision: 345122 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 58F0980539 X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-2.96 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-1.00)[-0.996,0]; NEURAL_HAM_SHORT(-0.97)[-0.969,0]; NEURAL_HAM_LONG(-1.00)[-0.999,0]; ASN(0.00)[asn:11403, ipnet:2610:1c1:1::/48, country:US] X-BeenThere: svn-src-stable@freebsd.org X-Mailman-Version: 2.1.29 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, 14 Mar 2019 00:58:40 -0000 Author: mav Date: Thu Mar 14 00:58:39 2019 New Revision: 345122 URL: https://svnweb.freebsd.org/changeset/base/345122 Log: MFC r344903: Improve entropy for ZFS taskqueue selection. I just found that at least on Skylake CPUs cpu_ticks() never returns odd values, only even, and possibly has even bigger step (176/2?), that makes its lower bits very bad entropy source, leaving half of taskqueues unused. Switch to sbinuptime(), closer to upstreams, mitigates the problem by the rate conversion working as kind of hash function. In case that is somehow not enough (timer rate is too low or too divisible) mix in curcpu. Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c ============================================================================== --- stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Thu Mar 14 00:57:54 2019 (r345121) +++ stable/12/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/spa.c Thu Mar 14 00:58:39 2019 (r345122) @@ -1070,7 +1070,8 @@ spa_taskq_dispatch_ent(spa_t *spa, zio_type_t t, zio_t tq = tqs->stqs_taskq[0]; } else { #ifdef _KERNEL - tq = tqs->stqs_taskq[cpu_ticks() % tqs->stqs_count]; + tq = tqs->stqs_taskq[(u_int)(sbinuptime() + curcpu) % + tqs->stqs_count]; #else tq = tqs->stqs_taskq[gethrtime() % tqs->stqs_count]; #endif