From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751484AbeCTWPU (ORCPT <rfc822;w@1wt.eu>);
        Tue, 20 Mar 2018 18:15:20 -0400
Received: from mail-pg0-f54.google.com ([74.125.83.54]:41506 "EHLO
        mail-pg0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751334AbeCTWPQ (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 20 Mar 2018 18:15:16 -0400
X-Google-Smtp-Source: AG47ELuCTZUBf4orh7A9FyCaf488tYm3Ts9/pKXikMm13N1wZEec2WQ2C6IvCuf5LPS95OApXQw2PQ==
Date: Tue, 20 Mar 2018 15:15:13 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
X-X-Sender: rientjes@chino.kir.corp.google.com
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
cc: Michal Hocko <mhocko@kernel.org>, "Li,Rongqing" <lirongqing@baidu.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
        "hannes@cmpxchg.org" <hannes@cmpxchg.org>
Subject: =?UTF-8?Q?Re=3A_=E7=AD=94=E5=A4=8D=3A_=E7=AD=94=E5=A4=8D=3A_=5BPATCH=5D_mm=2Fmemcontrol=2Ec=3A_speed_up_to_force_empty_a_memory_cgroup?=
In-Reply-To: <56508bd0-e8d7-55fd-5109-c8dacf26b13e@virtuozzo.com>
Message-ID: <alpine.DEB.2.20.1803201514340.14003@chino.kir.corp.google.com>
References: <1521448170-19482-1-git-send-email-lirongqing@baidu.com> <20180319085355.GQ23100@dhcp22.suse.cz> <2AD939572F25A448A3AE3CAEA61328C23745764B@BC-MAIL-M28.internal.baidu.com> <20180319103756.GV23100@dhcp22.suse.cz>
 <2AD939572F25A448A3AE3CAEA61328C2374589DC@BC-MAIL-M28.internal.baidu.com> <alpine.DEB.2.20.1803191044310.177918@chino.kir.corp.google.com> <20180320083950.GD23100@dhcp22.suse.cz> <alpine.DEB.2.20.1803201327060.167205@chino.kir.corp.google.com>
 <56508bd0-e8d7-55fd-5109-c8dacf26b13e@virtuozzo.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, 21 Mar 2018, Andrey Ryabinin wrote:

> >>> It would probably be best to limit the 
> >>> nr_pages to the amount that needs to be reclaimed, though, rather than 
> >>> over reclaiming.
> >>
> >> How do you achieve that? The charging path is not synchornized with the
> >> shrinking one at all.
> >>
> > 
> > The point is to get a better guess at how many pages, up to 
> > SWAP_CLUSTER_MAX, that need to be reclaimed instead of 1.
> > 
> >>> If you wanted to be invasive, you could change page_counter_limit() to 
> >>> return the count - limit, fix up the callers that look for -EBUSY, and 
> >>> then use max(val, SWAP_CLUSTER_MAX) as your nr_pages.
> >>
> >> I am not sure I understand
> >>
> > 
> > Have page_counter_limit() return the number of pages over limit, i.e. 
> > count - limit, since it compares the two anyway.  Fix up existing callers 
> > and then clamp that value to SWAP_CLUSTER_MAX in 
> > mem_cgroup_resize_limit().  It's a more accurate guess than either 1 or 
> > 1024.
> > 
> 
> JFYI, it's never 1, it's always SWAP_CLUSTER_MAX.
> See try_to_free_mem_cgroup_pages():
> ....	
> 	struct scan_control sc = {
> 		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
> 

Is SWAP_CLUSTER_MAX the best answer if I'm lowering the limit by 1GB?