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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 DF6CDC432C2 for ; Tue, 24 Sep 2019 22:36:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB5072146E for ; Tue, 24 Sep 2019 22:36:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388541AbfIXWgc (ORCPT ); Tue, 24 Sep 2019 18:36:32 -0400 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:59072 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389629AbfIXWgc (ORCPT ); Tue, 24 Sep 2019 18:36:32 -0400 Received: from dread.disaster.area (pa49-181-226-196.pa.nsw.optusnet.com.au [49.181.226.196]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id D3DC1363767; Wed, 25 Sep 2019 08:36:26 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.2) (envelope-from ) id 1iCtQ1-0005xQ-5W; Wed, 25 Sep 2019 08:36:25 +1000 Date: Wed, 25 Sep 2019 08:36:25 +1000 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 2/2] xfs: hard limit the background CIL push Message-ID: <20190924223625.GJ16973@dread.disaster.area> References: <20190909015159.19662-1-david@fromorbit.com> <20190909015159.19662-3-david@fromorbit.com> <20190916164255.GA2229799@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190916164255.GA2229799@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=FNpr/6gs c=1 sm=1 tr=0 a=dRuLqZ1tmBNts2YiI0zFQg==:117 a=dRuLqZ1tmBNts2YiI0zFQg==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=J70Eh1EUuV4A:10 a=20KFwNOVAAAA:8 a=7-415B0cAAAA:8 a=OLKw8n6I55EPgptPfn8A:9 a=JP6k1ayD4DNY8uaW:21 a=U2o874eqEwj4DYp9:21 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Mon, Sep 16, 2019 at 09:42:55AM -0700, Darrick J. Wong wrote: > On Mon, Sep 09, 2019 at 11:51:59AM +1000, Dave Chinner wrote: > > From: Dave Chinner > > > > In certain situations the background CIL push can be indefinitely > > delayed. While we have workarounds from the obvious cases now, it > > doesn't solve the underlying issue. This issue is that there is no > > upper limit on the CIL where we will either force or wait for > > a background push to start, hence allowing the CIL to grow without > > bound until it consumes all log space. > > > > To fix this, add a new wait queue to the CIL which allows background > > pushes to wait for the CIL context to be switched out. This happens > > when the push starts, so it will allow us to block incoming > > transaction commit completion until the push has started. This will > > only affect processes that are running modifications, and only when > > the CIL threshold has been significantly overrun. > > > > This has no apparent impact on performance, and doesn't even trigger > > until over 45 million inodes had been created in a 16-way fsmark > > test on a 2GB log. That was limiting at 64MB of log space used, so > > the active CIL size is only about 3% of the total log in that case. > > The concurrent removal of those files did not trigger the background > > sleep at all. > > > > Signed-off-by: Dave Chinner > > --- > > fs/xfs/xfs_log_cil.c | 30 +++++++++++++++++++++++++----- > > fs/xfs/xfs_log_priv.h | 1 + > > 2 files changed, 26 insertions(+), 5 deletions(-) > > > > diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c > > index ef652abd112c..eec9b32f5e08 100644 > > --- a/fs/xfs/xfs_log_cil.c > > +++ b/fs/xfs/xfs_log_cil.c > > @@ -670,6 +670,11 @@ xlog_cil_push( > > push_seq = cil->xc_push_seq; > > ASSERT(push_seq <= ctx->sequence); > > > > + /* > > + * Wake up any background push waiters now this context is being pushed. > > + */ > > + wake_up_all(&ctx->push_wait); > > + > > /* > > * Check if we've anything to push. If there is nothing, then we don't > > * move on to a new sequence number and so we have to be able to push > > @@ -746,6 +751,7 @@ xlog_cil_push( > > */ > > INIT_LIST_HEAD(&new_ctx->committing); > > INIT_LIST_HEAD(&new_ctx->busy_extents); > > + init_waitqueue_head(&new_ctx->push_wait); > > new_ctx->sequence = ctx->sequence + 1; > > new_ctx->cil = cil; > > cil->xc_ctx = new_ctx; > > @@ -898,7 +904,7 @@ xlog_cil_push_work( > > * checkpoint), but commit latency and memory usage limit this to a smaller > > * size. > > */ > > -static void > > +static bool > > xlog_cil_push_background( > > struct xlog *log) > > { > > @@ -915,14 +921,28 @@ xlog_cil_push_background( > > * space available yet. > > */ > > if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log)) > > - return; > > + return false; > > > > spin_lock(&cil->xc_push_lock); > > if (cil->xc_push_seq < cil->xc_current_sequence) { > > cil->xc_push_seq = cil->xc_current_sequence; > > queue_work(log->l_mp->m_cil_workqueue, &cil->xc_push_work); > > } > > + > > + /* > > + * If we are well over the space limit, throttle the work that is being > > + * done until the push work on this context has begun. This will prevent > > + * the CIL from violating maximum transaction size limits if the CIL > > + * push is delayed for some reason. > > + */ > > + if (cil->xc_ctx->space_used > XLOG_CIL_SPACE_LIMIT(log) * 2) { > > + up_read(&cil->xc_ctx_lock); > > + trace_printk("CIL space used %d", cil->xc_ctx->space_used); > > Needs a real tracepoint before this drops RFC status. Ok, that was just debugging stuff I forgot to remove, but I can turn it into a real tracepoint if you want. > > > + xlog_wait(&cil->xc_ctx->push_wait, &cil->xc_push_lock); > > + return true; > > + } > > spin_unlock(&cil->xc_push_lock); > > + return false; > > > > } > > > > @@ -1038,9 +1058,8 @@ xfs_log_commit_cil( > > if (lip->li_ops->iop_committing) > > lip->li_ops->iop_committing(lip, xc_commit_lsn); > > } > > - xlog_cil_push_background(log); > > - > > - up_read(&cil->xc_ctx_lock); > > + if (!xlog_cil_push_background(log)) > > + up_read(&cil->xc_ctx_lock); > > Hmmmm... the return value here tell us if ctx_lock has been dropped. > /me wonders if this would be cleaner if xlog_cil_push_background > returned having called up_read...? I thought about that - was on the fence about what to do. I'll change it to be unconditional. Cheers, Dave. -- Dave Chinner david@fromorbit.com