From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay3.corp.sgi.com [198.149.34.15]) by oss.sgi.com (Postfix) with ESMTP id 7E8197F58 for ; Mon, 26 May 2014 17:27:24 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay3.corp.sgi.com (Postfix) with ESMTP id 34F30AC003 for ; Mon, 26 May 2014 15:27:21 -0700 (PDT) Received: from ipmail07.adl2.internode.on.net (ipmail07.adl2.internode.on.net [150.101.137.131]) by cuda.sgi.com with ESMTP id j5oCvnha6XJkpJ3S for ; Mon, 26 May 2014 15:27:16 -0700 (PDT) Received: from disappointment.disaster.area ([192.168.1.110] helo=disappointment) by dastard with esmtp (Exim 4.80) (envelope-from ) id 1Wp3MA-0001PS-BV for xfs@oss.sgi.com; Tue, 27 May 2014 08:26:58 +1000 Received: from dave by disappointment with local (Exim 4.82) (envelope-from ) id 1Wp3MA-0002VA-Ao for xfs@oss.sgi.com; Tue, 27 May 2014 08:26:58 +1000 From: Dave Chinner Subject: [PATCH 1/2] xfs: block allocation work needs to be kswapd aware Date: Tue, 27 May 2014 08:26:53 +1000 Message-Id: <1401143214-9181-2-git-send-email-david@fromorbit.com> In-Reply-To: <1401143214-9181-1-git-send-email-david@fromorbit.com> References: <1401143214-9181-1-git-send-email-david@fromorbit.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com From: Dave Chinner Upon memory pressure, kswapd calls xfs_vm_writepage() from shrink_page_list(). This can result in delayed allocation occurring and that gets deferred to the the allocation workqueue. The allocation then runs outside kswapd context, which means if it needs memory (and it does to demand page metadata from disk) it can block in shrink_inactive_list() waiting for IO congestion. These blocking waits are normally avoiding in kswapd context, so under memory pressure writeback from kswapd can be arbitrarily delayed by memory reclaim. To avoid this, pass the kswapd context to the allocation being done by the workqueue, so that memory reclaim understands correctly that the work is being done for kswapd and therefore it is not blocked and does not delay memory reclaim. To avoid issues with int->char conversion of flag fields (as noticed in v1 of this patch) convert the flag fields in the struct xfs_bmalloca to bool types. pahole indicates these variables are still single byte variables, so no extra space is consumed by this change. cc: Reported-by: Tetsuo Handa Signed-off-by: Dave Chinner --- fs/xfs/xfs_bmap_util.c | 16 +++++++++++++--- fs/xfs/xfs_bmap_util.h | 13 +++++++------ 2 files changed, 20 insertions(+), 9 deletions(-) diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index 057f671..703b3ec 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -258,14 +258,23 @@ xfs_bmapi_allocate_worker( struct xfs_bmalloca *args = container_of(work, struct xfs_bmalloca, work); unsigned long pflags; + unsigned long new_pflags = PF_FSTRANS; - /* we are in a transaction context here */ - current_set_flags_nested(&pflags, PF_FSTRANS); + /* + * we are in a transaction context here, but may also be doing work + * in kswapd context, and hence we may need to inherit that state + * temporarily to ensure that we don't block waiting for memory reclaim + * in any way. + */ + if (args->kswapd) + new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; + + current_set_flags_nested(&pflags, new_pflags); args->result = __xfs_bmapi_allocate(args); complete(args->done); - current_restore_flags_nested(&pflags, PF_FSTRANS); + current_restore_flags_nested(&pflags, new_pflags); } /* @@ -284,6 +293,7 @@ xfs_bmapi_allocate( args->done = &done; + args->kswapd = current_is_kswapd(); INIT_WORK_ONSTACK(&args->work, xfs_bmapi_allocate_worker); queue_work(xfs_alloc_wq, &args->work); wait_for_completion(&done); diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h index 935ed2b..075f722 100644 --- a/fs/xfs/xfs_bmap_util.h +++ b/fs/xfs/xfs_bmap_util.h @@ -50,12 +50,13 @@ struct xfs_bmalloca { xfs_extlen_t total; /* total blocks needed for xaction */ xfs_extlen_t minlen; /* minimum allocation size (blocks) */ xfs_extlen_t minleft; /* amount must be left after alloc */ - char eof; /* set if allocating past last extent */ - char wasdel; /* replacing a delayed allocation */ - char userdata;/* set if is user data */ - char aeof; /* allocated space at eof */ - char conv; /* overwriting unwritten extents */ - char stack_switch; + bool eof; /* set if allocating past last extent */ + bool wasdel; /* replacing a delayed allocation */ + bool userdata;/* set if is user data */ + bool aeof; /* allocated space at eof */ + bool conv; /* overwriting unwritten extents */ + bool stack_switch; + bool kswapd; /* allocation in kswapd context */ int flags; struct completion *done; struct work_struct work; -- 1.9.0 _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs