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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, 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 96C36C43331 for ; Thu, 26 Mar 2020 05:26:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59A1A20719 for ; Thu, 26 Mar 2020 05:26:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="gHUDdgQh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725854AbgCZF0o (ORCPT ); Thu, 26 Mar 2020 01:26:44 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:51814 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725842AbgCZF0o (ORCPT ); Thu, 26 Mar 2020 01:26:44 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02Q5OJEY038818; Thu, 26 Mar 2020 05:26:39 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=corp-2020-01-29; bh=9Vv7eD1kf/bHliIuhvDdXknTxRcG12j6NIFpbLfKvrc=; b=gHUDdgQhQZPbhXmOVT1lznSZwHaILp4u4QUTJ6kBqXlYqhPGtkS+XFpoxXF5AziBvTk9 KGukhj1pcbZgJBR3A8RQfR4v3Ish0LgIIzbrvslE44Q2O+vbF5Iv9T6qXovzdIgWNCUr HRvHOsqxHnRLghNKWQTdPru5kBagoKYp71gR/0P6rxNeGjIu34Q91c0XK9b8JbjGce8V 09fdc5z3MdlnpfeRRBP2ID+/INE1alqypngq7vdtkmhua5YQKq0OJWGgEWOx8Tohdkl8 +Vq1zikUuCEzAuekNIMkwNCNQ9I56kkqb5heOAqiRQD2UMXL8cvj0nEys+khREAZdX5J Sw== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by userp2120.oracle.com with ESMTP id 3005kvcjha-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 26 Mar 2020 05:26:38 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 02Q5LsUu180541; Thu, 26 Mar 2020 05:24:38 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3030.oracle.com with ESMTP id 3006r7tqdr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 26 Mar 2020 05:24:38 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 02Q5OaWA019839; Thu, 26 Mar 2020 05:24:36 GMT Received: from localhost (/10.159.237.96) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 25 Mar 2020 22:24:36 -0700 Date: Wed, 25 Mar 2020 22:24:35 -0700 From: "Darrick J. Wong" To: Dave Chinner , Brian Foster Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 2/8] xfs: Throttle commits on delayed background CIL push Message-ID: <20200326052435.GK29351@magnolia> References: <20200325014205.11843-1-david@fromorbit.com> <20200325014205.11843-3-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200325014205.11843-3-david@fromorbit.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9571 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 adultscore=0 suspectscore=0 phishscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003260034 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9571 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 bulkscore=0 phishscore=0 suspectscore=0 impostorscore=0 spamscore=0 adultscore=0 priorityscore=1501 mlxlogscore=999 lowpriorityscore=0 mlxscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003260034 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Mar 25, 2020 at 12:41:59PM +1100, 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 > Reviewed-by: Brian Foster This looks reasonable to me, though considering the big long thread that erupted a few versions ago I'm seriously wondering what he thinks of all this? Reviewed-by: Darrick J. Wong --D > --- > fs/xfs/xfs_log_cil.c | 37 +++++++++++++++++++++++++++++++++---- > fs/xfs/xfs_log_priv.h | 24 ++++++++++++++++++++++++ > fs/xfs/xfs_trace.h | 1 + > 3 files changed, 58 insertions(+), 4 deletions(-) > > diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c > index 27de462d2ba40..ac43301ae2f43 100644 > --- a/fs/xfs/xfs_log_cil.c > +++ b/fs/xfs/xfs_log_cil.c > @@ -668,6 +668,11 @@ xlog_cil_push_work( > 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 > @@ -744,6 +749,7 @@ xlog_cil_push_work( > */ > 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; > @@ -891,7 +897,7 @@ xlog_cil_push_work( > */ > static void > xlog_cil_push_background( > - struct xlog *log) > + struct xlog *log) __releases(cil->xc_ctx_lock) > { > struct xfs_cil *cil = log->l_cilp; > > @@ -905,14 +911,36 @@ xlog_cil_push_background( > * don't do a background push if we haven't used up all the > * space available yet. > */ > - if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log)) > + if (cil->xc_ctx->space_used < XLOG_CIL_SPACE_LIMIT(log)) { > + up_read(&cil->xc_ctx_lock); > return; > + } > > 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); > } > + > + /* > + * Drop the context lock now, we can't hold that if we need to sleep > + * because we are over the blocking threshold. The push_lock is still > + * held, so blocking threshold sleep/wakeup is still correctly > + * serialised here. > + */ > + up_read(&cil->xc_ctx_lock); > + > + /* > + * If we are well over the space limit, throttle the work that is being > + * done until the push work on this context has begun. > + */ > + if (cil->xc_ctx->space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log)) { > + trace_xfs_log_cil_wait(log, cil->xc_ctx->ticket); > + ASSERT(cil->xc_ctx->space_used < log->l_logsize); > + xlog_wait(&cil->xc_ctx->push_wait, &cil->xc_push_lock); > + return; > + } > + > spin_unlock(&cil->xc_push_lock); > > } > @@ -1032,9 +1060,9 @@ 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); > + /* xlog_cil_push_background() releases cil->xc_ctx_lock */ > + xlog_cil_push_background(log); > } > > /* > @@ -1193,6 +1221,7 @@ xlog_cil_init( > > INIT_LIST_HEAD(&ctx->committing); > INIT_LIST_HEAD(&ctx->busy_extents); > + init_waitqueue_head(&ctx->push_wait); > ctx->sequence = 1; > ctx->cil = cil; > cil->xc_ctx = ctx; > diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h > index 8c4be91f62d0d..dacab1817a1b0 100644 > --- a/fs/xfs/xfs_log_priv.h > +++ b/fs/xfs/xfs_log_priv.h > @@ -240,6 +240,7 @@ struct xfs_cil_ctx { > struct xfs_log_vec *lv_chain; /* logvecs being pushed */ > struct list_head iclog_entry; > struct list_head committing; /* ctx committing list */ > + wait_queue_head_t push_wait; /* background push throttle */ > struct work_struct discard_endio_work; > }; > > @@ -337,10 +338,33 @@ struct xfs_cil { > * buffer window (32MB) as measurements have shown this to be roughly the > * point of diminishing performance increases under highly concurrent > * modification workloads. > + * > + * To prevent the CIL from overflowing upper commit size bounds, we introduce a > + * new threshold at which we block committing transactions until the background > + * CIL commit commences and switches to a new context. While this is not a hard > + * limit, it forces the process committing a transaction to the CIL to block and > + * yeild the CPU, giving the CIL push work a chance to be scheduled and start > + * work. This prevents a process running lots of transactions from overfilling > + * the CIL because it is not yielding the CPU. We set the blocking limit at > + * twice the background push space threshold so we keep in line with the AIL > + * push thresholds. > + * > + * Note: this is not a -hard- limit as blocking is applied after the transaction > + * is inserted into the CIL and the push has been triggered. It is largely a > + * throttling mechanism that allows the CIL push to be scheduled and run. A hard > + * limit will be difficult to implement without introducing global serialisation > + * in the CIL commit fast path, and it's not at all clear that we actually need > + * such hard limits given the ~7 years we've run without a hard limit before > + * finding the first situation where a checkpoint size overflow actually > + * occurred. Hence the simple throttle, and an ASSERT check to tell us that > + * we've overrun the max size. > */ > #define XLOG_CIL_SPACE_LIMIT(log) \ > min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4) > > +#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \ > + (XLOG_CIL_SPACE_LIMIT(log) * 2) > + > /* > * ticket grant locks, queues and accounting have their own cachlines > * as these are quite hot and can be operated on concurrently. > diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h > index fbfdd9cf160df..575ca74532f79 100644 > --- a/fs/xfs/xfs_trace.h > +++ b/fs/xfs/xfs_trace.h > @@ -1015,6 +1015,7 @@ DEFINE_LOGGRANT_EVENT(xfs_log_ticket_regrant_sub); > DEFINE_LOGGRANT_EVENT(xfs_log_ticket_done); > DEFINE_LOGGRANT_EVENT(xfs_log_ticket_done_sub); > DEFINE_LOGGRANT_EVENT(xfs_log_ticket_done_exit); > +DEFINE_LOGGRANT_EVENT(xfs_log_cil_wait); > > DECLARE_EVENT_CLASS(xfs_log_item_class, > TP_PROTO(struct xfs_log_item *lip), > -- > 2.26.0.rc2 >