From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:35284 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759271AbdADKHK (ORCPT ); Wed, 4 Jan 2017 05:07:10 -0500 Subject: Patch "mm/vmscan.c: set correct defer count for shrinker" has been added to the 4.8-stable tree To: shli@fb.com, akpm@linux-foundation.org, gregkh@linuxfoundation.org, hannes@cmpxchg.org, mhocko@kernel.org, torvalds@linux-foundation.org, vdavydov@parallels.com Cc: , From: Date: Wed, 04 Jan 2017 11:07:07 +0100 Message-ID: <14835244272287@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled mm/vmscan.c: set correct defer count for shrinker to the 4.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-vmscan.c-set-correct-defer-count-for-shrinker.patch and it can be found in the queue-4.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 5f33a0803bbd781de916f5c7448cbbbbc763d911 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Mon, 12 Dec 2016 16:41:50 -0800 Subject: mm/vmscan.c: set correct defer count for shrinker From: Shaohua Li commit 5f33a0803bbd781de916f5c7448cbbbbc763d911 upstream. Our system uses significantly more slab memory with memcg enabled with the latest kernel. With 3.10 kernel, slab uses 2G memory, while with 4.6 kernel, 6G memory is used. The shrinker has problem. Let's see we have two memcg for one shrinker. In do_shrink_slab: 1. Check cg1. nr_deferred = 0, assume total_scan = 700. batch size is 1024, then no memory is freed. nr_deferred = 700 2. Check cg2. nr_deferred = 700. Assume freeable = 20, then total_scan = 10 or 40. Let's assume it's 10. No memory is freed. nr_deferred = 10. The deferred share of cg1 is lost in this case. kswapd will free no memory even run above steps again and again. The fix makes sure one memcg's deferred share isn't lost. Link: http://lkml.kernel.org/r/2414be961b5d25892060315fbb56bb19d81d0c07.1476227351.git.shli@fb.com Signed-off-by: Shaohua Li Cc: Johannes Weiner Cc: Michal Hocko Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/vmscan.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -291,6 +291,7 @@ static unsigned long do_shrink_slab(stru int nid = shrinkctl->nid; long batch_size = shrinker->batch ? shrinker->batch : SHRINK_BATCH; + long scanned = 0, next_deferred; freeable = shrinker->count_objects(shrinker, shrinkctl); if (freeable == 0) @@ -312,7 +313,9 @@ static unsigned long do_shrink_slab(stru pr_err("shrink_slab: %pF negative objects to delete nr=%ld\n", shrinker->scan_objects, total_scan); total_scan = freeable; - } + next_deferred = nr; + } else + next_deferred = total_scan; /* * We need to avoid excessive windup on filesystem shrinkers @@ -369,17 +372,22 @@ static unsigned long do_shrink_slab(stru count_vm_events(SLABS_SCANNED, nr_to_scan); total_scan -= nr_to_scan; + scanned += nr_to_scan; cond_resched(); } + if (next_deferred >= scanned) + next_deferred -= scanned; + else + next_deferred = 0; /* * move the unused scan count back into the shrinker in a * manner that handles concurrent updates. If we exhausted the * scan, there is no need to do an update. */ - if (total_scan > 0) - new_nr = atomic_long_add_return(total_scan, + if (next_deferred > 0) + new_nr = atomic_long_add_return(next_deferred, &shrinker->nr_deferred[nid]); else new_nr = atomic_long_read(&shrinker->nr_deferred[nid]); Patches currently in stable-queue which might be from shli@fb.com are queue-4.8/mm-vmscan.c-set-correct-defer-count-for-shrinker.patch