From owner-svn-src-all@freebsd.org Fri Aug 25 08:20:42 2017 Return-Path: Delivered-To: svn-src-all@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 47C1EDF2E50 for ; Fri, 25 Aug 2017 08:20:42 +0000 (UTC) (envelope-from freebsd-listen@fabiankeil.de) Received: from smtprelay05.ispgateway.de (smtprelay05.ispgateway.de [80.67.31.98]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 0DD3A7C675; Fri, 25 Aug 2017 08:20:41 +0000 (UTC) (envelope-from freebsd-listen@fabiankeil.de) Received: from [78.35.148.132] (helo=fabiankeil.de) by smtprelay05.ispgateway.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1dl9ol-0003JY-To; Fri, 25 Aug 2017 10:18:15 +0200 Date: Fri, 25 Aug 2017 10:16:47 +0200 From: Fabian Keil To: Warner Losh Cc: svn-src-all@freebsd.org Subject: Re: svn commit: r322863 - head/sys/cam Message-ID: <20170825101647.5a385e1c@fabiankeil.de> In-Reply-To: <201708242211.v7OMBAlc012582@repo.freebsd.org> References: <201708242211.v7OMBAlc012582@repo.freebsd.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/LWaf+IfUL2+zVwlmID+qDJV"; protocol="application/pgp-signature" X-Df-Sender: Nzc1MDY3 X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Aug 2017 08:20:42 -0000 --Sig_/LWaf+IfUL2+zVwlmID+qDJV Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Warner Losh wrote: > Author: imp > Date: Thu Aug 24 22:11:10 2017 > New Revision: 322863 > URL: https://svnweb.freebsd.org/changeset/base/322863 >=20 > Log: > Expand the latency tracking array from 1.024s to 8.192s to help track > extreme outliers from dodgy drives. Adjust comments to reflect this, > and make sure that the number of latency buckets match in the two > places where it matters. It also matters for the sysctl description in cam_iosched_iop_stats_sysctl_= init(). Would you mind increasing LAT_BUCKETS a bit more? I've recently set it to 17 in ElectroBSD as writes to my laptop's disk occasionally take a while under load: fk@t520 ~ $sudo /usr/src/share/dtrace/bio-request-latency [...] ada0 BIO_WRITE value ------------- Distribution ------------- count 16 | 0 32 | 1 64 | 34 128 |@ 582 256 |@@@@@@@@@@ 10608 512 |@@@@@ 5574 1024 |@@ 2454 2048 |@@@@ 3872 4096 |@@@@ 4043 8192 |@@@@ 4115 16384 |@@@@@ 4953 32768 |@@@ 3656 65536 |@@ 2252 131072 |@ 764 262144 | 331 524288 | 291 1048576 | 53 2097152 | 9 4194304 | 4 8388608 | 6 16777216 | 2 33554432 | 0 ada0 BIO_READ value ------------- Distribution ------------- count 16 | 0 32 | 1 64 | 126 128 |@ 1205 256 |@@@@@ 6359 512 |@@@ 3987 1024 |@@ 2044 2048 |@ 1384 4096 |@@ 2853 8192 |@@@@@ 6012 16384 |@@@@@@ 7254 32768 |@@@@@ 6524 65536 |@@@@ 4945 131072 |@@@ 3006 262144 |@ 1194 524288 |@ 620 1048576 | 162 2097152 | 0 Disk Bio Type Requests | Latency in us = | iops Throughput | avg stddev max min | ada0 BIO_FLUSH 253 | 145927 162796 1253731 10293 = | 0 0 k/s ada0 BIO_WRITE 43604 | 30345 261090 30069820 61 = | 43 1994 k/s ada0 BIO_READ 47676 | 56039 128083 1691813 63 = | 47 1260 k/s While proper tuning helps, the latency stats are also useful on systems where the iosched limiters haven't been enabled (yet). Fabian --Sig_/LWaf+IfUL2+zVwlmID+qDJV Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iF0EARECAB0WIQTKUNd6H/m3+ByGULIFiohV/3dUnQUCWZ/c7wAKCRAFiohV/3dU nfxrAKCfoLPKVLoyATS9U5izZE90l/nPEACgvaCQaQqjVi0JDYeb/ULD7gwcEQ0= =ZKXA -----END PGP SIGNATURE----- --Sig_/LWaf+IfUL2+zVwlmID+qDJV--