linux-kernel - Re: [PATCH] mm, swap: Make VMA based swap readahead configurable

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Message-ID: <CAC=cRTMMHX1SqPygkh+4scmhQhv3=kZMJAFf=EhZZU9S2006JA@mail.gmail.com>
Date:   Fri, 6 Oct 2017 20:28:59 +0800
From:   huang ying <huang.ying.caritas@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Michal Hocko <mhocko@...nel.org>,
        Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Rik van Riel <riel@...hat.com>, Shaohua Li <shli@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Tim Chen <tim.c.chen@...el.com>
Subject: Re: [PATCH] mm, swap: Make VMA based swap readahead configurable

On Tue, Oct 3, 2017 at 5:49 AM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Mon, 2 Oct 2017 08:45:40 -0700 Dave Hansen <dave.hansen@...el.com> wrote:
>
>> On 09/27/2017 06:02 PM, Huang, Ying wrote:
>> > I still think there may be a performance regression for some users
>> > because of the change of the algorithm and the knobs, and the
>> > performance regression can be resolved via setting the new knob.  But I
>> > don't think there will be a functionality regression.  Do you agree?
>>
>> A performance regression is a regression.  I don't understand why we are
>> splitting hairs as to what kind of regression it is.
>>
>
> Yes.
>
> Ying, please find us a way of avoiding any disruption to existing
> system setups.  One which doesn't require that the operator perform a
> configuration change to restore prior behaviour/performance.

Sorry for late.  I am in holiday recently.

OK.  For me, I think the most clean way is to use page_cluster to
control both the virtual and physical swap readahead.  If you are OK
with that, I will prepare the patch.

> And please let's get this done well in advance of the 4.14 release.

Sure.

Best Regards,
Huang, Ying