From owner-svn-src-head@freebsd.org Mon Oct 26 04:04:07 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 618AB438FC5; Mon, 26 Oct 2020 04:04:07 +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) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 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 4CKLn31gzLz4vSd; Mon, 26 Oct 2020 04:04:07 +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 1D10614D36; Mon, 26 Oct 2020 04:04:07 +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 09Q4460e021251; Mon, 26 Oct 2020 04:04:06 GMT (envelope-from mav@FreeBSD.org) Received: (from mav@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 09Q446wQ021250; Mon, 26 Oct 2020 04:04:06 GMT (envelope-from mav@FreeBSD.org) Message-Id: <202010260404.09Q446wQ021250@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mav set sender to mav@FreeBSD.org using -f From: Alexander Motin Date: Mon, 26 Oct 2020 04:04:06 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r367052 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mav X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 367052 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Oct 2020 04:04:07 -0000 Author: mav Date: Mon Oct 26 04:04:06 2020 New Revision: 367052 URL: https://svnweb.freebsd.org/changeset/base/367052 Log: Enable bioq 'car limit' added at r335066 at 128 bios. Without the 'car limit' enabled (before this), running sequential ZFS scrub on HDD without command queuing support, I've measured latency on concurrent random reads reaching 4 seconds (surprised that not more). Enabling this reduced the latency to 65 milliseconds, while scrub still doing ~180MB/s. For disks with command queuing this does not make much difference (if any), since most time all the requests are queued down to the disk or HBA, leaving nothing in the queue to sort. And even if something does not fit, staying on the queue, it is likely not for long. To not limit sorting in such bursty scenarios I've added batched counter zeroing when the queue is getting empty. The internal scheduler of the SAS HDD I was testing seems to be even more loyal to random I/O, reducing the scrub speed to ~120MB/s. So in case somebody worried this is limit is too strict -- it actually looks relaxed. MFC after: 2 weeks Sponsored by: iXsystems, Inc. Modified: head/sys/kern/subr_disk.c Modified: head/sys/kern/subr_disk.c ============================================================================== --- head/sys/kern/subr_disk.c Mon Oct 26 03:26:18 2020 (r367051) +++ head/sys/kern/subr_disk.c Mon Oct 26 04:04:06 2020 (r367052) @@ -26,7 +26,7 @@ __FBSDID("$FreeBSD$"); #include #include -static int bioq_batchsize = 0; +static int bioq_batchsize = 128; SYSCTL_INT(_debug, OID_AUTO, bioq_batchsize, CTLFLAG_RW, &bioq_batchsize, 0, "BIOQ batch size"); @@ -172,6 +172,8 @@ bioq_remove(struct bio_queue_head *head, struct bio *b head->insert_point = NULL; TAILQ_REMOVE(&head->queue, bp, bio_queue); + if (TAILQ_EMPTY(&head->queue)) + head->batched = 0; head->total--; }