From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E17A1ECE597 for ; Wed, 9 Oct 2019 03:22:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A27D5206C2 for ; Wed, 9 Oct 2019 03:22:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A27D5206C2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=fromorbit.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DE76A8E0015; Tue, 8 Oct 2019 23:21:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B254F8E001A; Tue, 8 Oct 2019 23:21:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5E9B58E0010; Tue, 8 Oct 2019 23:21:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0192.hostedemail.com [216.40.44.192]) by kanga.kvack.org (Postfix) with ESMTP id 19C1D8E0014 for ; Tue, 8 Oct 2019 23:21:34 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id B2873824CA3B for ; Wed, 9 Oct 2019 03:21:33 +0000 (UTC) X-FDA: 76022796066.19.ring32_2aa243ef1800a X-HE-Tag: ring32_2aa243ef1800a X-Filterd-Recvd-Size: 5980 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Wed, 9 Oct 2019 03:21:32 +0000 (UTC) Received: from dread.disaster.area (pa49-181-226-196.pa.nsw.optusnet.com.au [49.181.226.196]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 3F99E43EC20; Wed, 9 Oct 2019 14:21:27 +1100 (AEDT) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92.2) (envelope-from ) id 1iI2XW-0006B2-La; Wed, 09 Oct 2019 14:21:26 +1100 Received: from dave by discord.disaster.area with local (Exim 4.92) (envelope-from ) id 1iI2XW-00038w-JB; Wed, 09 Oct 2019 14:21:26 +1100 From: Dave Chinner To: linux-xfs@vger.kernel.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 01/26] xfs: Lower CIL flush limit for large logs Date: Wed, 9 Oct 2019 14:20:59 +1100 Message-Id: <20191009032124.10541-2-david@fromorbit.com> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20191009032124.10541-1-david@fromorbit.com> References: <20191009032124.10541-1-david@fromorbit.com> MIME-Version: 1.0 X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=P6RKvmIu c=1 sm=1 tr=0 a=dRuLqZ1tmBNts2YiI0zFQg==:117 a=dRuLqZ1tmBNts2YiI0zFQg==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=XobE76Q3jBoA:10 a=20KFwNOVAAAA:8 a=UuDO-KUg2xYWwgiXHJ0A:9 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Dave Chinner The current CIL size aggregation limit is 1/8th the log size. This means for large logs we might be aggregating at least 250MB of dirty obje= cts in memory before the CIL is flushed to the journal. With CIL shadow buffers sitting around, this means the CIL is often consuming >500MB of temporary memory that is all allocated under GFP_NOFS conditions. Flushing the CIL can take some time to do if there is other IO ongoing, and can introduce substantial log force latency by itself. It also pins the memory until the objects are in the AIL and can be written back and reclaimed by shrinkers. Hence this threshold also tends to determine the minimum amount of memory XFS can operate in under heavy modification without triggering the OOM killer. Modify the CIL space limit to prevent such huge amounts of pinned metadata from aggregating. We can have 2MB of log IO in flight at once, so limit aggregation to 16x this size. This threshold was chosen as it little impact on performance (on 16-way fsmark) or log traffic but pins a lot less memory on large logs especially under heavy memory pressure. An aggregation limit of 8x had 5-10% performance degradation and a 50% increase in log throughput for the same workload, so clearly that was too small for highly concurrent workloads on large logs. This was found via trace analysis of AIL behaviour. e.g. insertion from a single CIL flush: xfs_ail_insert: old lsn 0/0 new lsn 1/3033090 type XFS_LI_INODE flags IN_= AIL $ grep xfs_ail_insert /mnt/scratch/s.t |grep "new lsn 1/3033090" |wc -l 1721823 $ So there were 1.7 million objects inserted into the AIL from this CIL checkpoint, the first at 2323.392108, the last at 2325.667566 which was the end of the trace (i.e. it hadn't finished). Clearly a major problem. Signed-off-by: Dave Chinner --- fs/xfs/xfs_log_priv.h | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h index b880c23cb6e4..a3cc8a9a16d9 100644 --- a/fs/xfs/xfs_log_priv.h +++ b/fs/xfs/xfs_log_priv.h @@ -323,13 +323,30 @@ struct xfs_cil { * tries to keep 25% of the log free, so we need to keep below that limi= t or we * risk running out of free log space to start any new transactions. * - * In order to keep background CIL push efficient, we will set a lower - * threshold at which background pushing is attempted without blocking c= urrent - * transaction commits. A separate, higher bound defines when CIL pushe= s are - * enforced to ensure we stay within our maximum checkpoint size bounds. - * threshold, yet give us plenty of space for aggregation on large logs. + * In order to keep background CIL push efficient, we only need to ensur= e the + * CIL is large enough to maintain sufficient in-memory relogging to avo= id + * repeated physical writes of frequently modified metadata. If we allow= the CIL + * to grow to a substantial fraction of the log, then we may be pinning = hundreds + * of megabytes of metadata in memory until the CIL flushes. This can ca= use + * issues when we are running low on memory - pinned memory cannot be re= claimed, + * and the CIL consumes a lot of memory. Hence we need to set an upper p= hysical + * size limit for the CIL that limits the maximum amount of memory pinne= d by the + * CIL but does not limit performance by reducing relogging efficiency + * significantly. + * + * As such, the CIL push threshold ends up being the smaller of two thre= sholds: + * - a threshold large enough that it allows CIL to be pushed and progre= ss to be + * made without excessive blocking of incoming transaction commits. Th= is is + * defined to be 12.5% of the log space - half the 25% push threshold = of the + * AIL. + * - small enough that it doesn't pin excessive amounts of memory but ma= intains + * close to peak relogging efficiency. This is defined to be 16x the i= clog + * buffer window (32MB) as measurements have shown this to be roughly = the + * point of diminishing performance increases under highly concurrent + * modification workloads. */ -#define XLOG_CIL_SPACE_LIMIT(log) (log->l_logsize >> 3) +#define XLOG_CIL_SPACE_LIMIT(log) \ + min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4= ) =20 /* * ticket grant locks, queues and accounting have their own cachlines --=20 2.23.0.rc1