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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A351DC4332F for ; Wed, 17 Nov 2021 05:53:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9003860E08 for ; Wed, 17 Nov 2021 05:53:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233436AbhKQF4P (ORCPT ); Wed, 17 Nov 2021 00:56:15 -0500 Received: from mail109.syd.optusnet.com.au ([211.29.132.80]:49075 "EHLO mail109.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233348AbhKQF4O (ORCPT ); Wed, 17 Nov 2021 00:56:14 -0500 Received: from dread.disaster.area (pa49-195-103-97.pa.nsw.optusnet.com.au [49.195.103.97]) by mail109.syd.optusnet.com.au (Postfix) with ESMTPS id EC51AA46A9; Wed, 17 Nov 2021 16:53:13 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1mnDsd-009nSO-AO; Wed, 17 Nov 2021 16:53:11 +1100 Date: Wed, 17 Nov 2021 16:53:11 +1100 From: Dave Chinner To: NeilBrown Cc: Andrew Morton , Michal Hocko , Theodore Ts'o , linux-ext4@vger.kernel.org, Jaegeuk Kim , Chao Yu , "Darrick J. Wong" , linux-xfs@vger.kernel.org, Chuck Lever , linux-f2fs-devel@lists.sourceforge.net, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] MM: introduce memalloc_retry_wait() Message-ID: <20211117055311.GS449541@dread.disaster.area> References: <163712329077.13692.12796971766360881401@noble.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <163712329077.13692.12796971766360881401@noble.neil.brown.name> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=e9dl9Yl/ c=1 sm=1 tr=0 ts=619498ca a=fP9RlOTWD4uZJjPSFnn6Ew==:117 a=fP9RlOTWD4uZJjPSFnn6Ew==:17 a=kj9zAlcOel0A:10 a=vIxV3rELxO4A:10 a=7-415B0cAAAA:8 a=WAyi4Cf-4lf-hVXyuRgA:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 17, 2021 at 03:28:10PM +1100, NeilBrown wrote: > > Various places in the kernel - largely in filesystems - respond to a > memory allocation failure by looping around and re-trying. ..... > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index aca874d33fe6..f2f2a5b28808 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -214,6 +214,27 @@ static inline void fs_reclaim_acquire(gfp_t gfp_mask) { } > static inline void fs_reclaim_release(gfp_t gfp_mask) { } > #endif > > +/* Any memory-allocation retry loop should use > + * memalloc_retry_wait(), and pass the flags for the most > + * constrained allocation attempt that might have failed. > + * This provides useful documentation of where loops are, > + * and a central place to fine tune the waiting as the MM > + * implementation changes. > + */ > +static inline void memalloc_retry_wait(gfp_t gfp_flags) > +{ > + gfp_flags = current_gfp_context(gfp_flags); > + if ((gfp_flags & __GFP_DIRECT_RECLAIM) && > + !(gfp_flags & __GFP_NORETRY)) > + /* Probably waited already, no need for much more */ > + schedule_timeout_uninterruptible(1); > + else > + /* Probably didn't wait, and has now released a lock, > + * so now is a good time to wait > + */ > + schedule_timeout_uninterruptible(HZ/50); > +} The existing congestion_wait() calls io_schedule_timeout() under TASK_UNINTERRUPTIBLE conditions. Does changing all these calls just to a plain schedule_timeout_uninterruptible() make any difference to behaviour? At least process accounting will appear different (uninterruptible sleep instead of IO wait), and I suspect that the block plug flushing in io_schedule() might be a good idea to retain for all the filesystems that call this function from IO-related routines. Cheers, Dave. -- Dave Chinner david@fromorbit.com