From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754168AbbGQWmo (ORCPT ); Fri, 17 Jul 2015 18:42:44 -0400 Received: from mail-pd0-f180.google.com ([209.85.192.180]:34317 "EHLO mail-pd0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752225AbbGQWmn (ORCPT ); Fri, 17 Jul 2015 18:42:43 -0400 Date: Sat, 18 Jul 2015 07:42:33 +0900 From: Minchan Kim To: Sergey Senozhatsky Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sergey Senozhatsky 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> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 is outdated in general case, by design.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