From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 4869D280344 for ; Fri, 17 Jul 2015 18:42:45 -0400 (EDT) Received: by pactm7 with SMTP id tm7so67964960pac.2 for ; Fri, 17 Jul 2015 15:42:45 -0700 (PDT) Received: from mail-pd0-x231.google.com (mail-pd0-x231.google.com. [2607:f8b0:400e:c02::231]) by mx.google.com with ESMTPS id da5si20762716pbc.20.2015.07.17.15.42.42 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 17 Jul 2015 15:42:43 -0700 (PDT) Received: by pdbqm3 with SMTP id qm3so68301808pdb.0 for ; Fri, 17 Jul 2015 15:42:42 -0700 (PDT) Date: Sat, 18 Jul 2015 07:42:33 +0900 From: Minchan Kim Subject: Re: [PATCH v2] zsmalloc: do not take class lock in zs_shrinker_count() Message-ID: <20150717224233.GA7334@blaptop> References: <1437131898-2231-1-git-send-email-sergey.senozhatsky@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1437131898-2231-1-git-send-email-sergey.senozhatsky@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Sergey Senozhatsky Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sergey Senozhatsky Hi Sergey, On Fri, Jul 17, 2015 at 08:18:18PM +0900, Sergey Senozhatsky wrote: > We can avoid taking class ->lock around zs_can_compact() in > zs_shrinker_count(), because the number that we return back > is outdated in general case, by design. We have different > sources that are able to change class's state right after we > return from zs_can_compact() -- ongoing I/O operations, manually > triggered compaction, or two of them happening simultaneously. > > We re-do this calculations during compaction on a per class basis > anyway. > > zs_unregister_shrinker() will not return until we have an > active shrinker, so classes won't unexpectedly disappear > while zs_shrinker_count() iterates them. > > Signed-off-by: Sergey Senozhatsky I asked to remove the comment of zs_can_compact about lock. "Should be called under class->lock." Otherwise, Acked-by: Minchan Kim > --- > mm/zsmalloc.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index 1edd8a0..ed64cf5 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -1836,9 +1836,7 @@ static unsigned long zs_shrinker_count(struct shrinker *shrinker, > if (class->index != i) > continue; > > - spin_lock(&class->lock); > pages_to_free += zs_can_compact(class); > - spin_unlock(&class->lock); > } > > return pages_to_free; > -- > 2.4.6 > -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org