linux-kernel - Re: [RFC PATCH 0/2] mm/vmstat: Reduce zone lock hold time when reading /proc/pagetypeinfo

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Date:   Thu, 24 Oct 2019 12:16:34 -0400
From:   Waiman Long <longman@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>
Cc:     Johannes Weiner <hannes@...xchg.org>, Roman Gushchin <guro@...com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Jann Horn <jannh@...gle.com>, Song Liu <songliubraving@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rafael Aquini <aquini@...hat.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/2] mm/vmstat: Reduce zone lock hold time when
 reading /proc/pagetypeinfo

On 10/24/19 4:20 AM, Michal Hocko wrote:
> On Wed 23-10-19 12:27:35, Michal Hocko wrote:
> [...]
>> I went with a bound to the pages iteratred over in the free_list. See
>> patch 2.
> I will fold http://lkml.kernel.org/r/20191023180121.GN17610@dhcp22.suse.cz
> to patch 2 unless there are any objections. If there are no further
> comments I will send the two patches without an RFC tomorrow.
>
> Thanks for all the feedback.

I am fine with your change. My concern is to make sure that there is a
reasonable bound to the worst case scenario. With that change, the upper
bound is iterating 100,000 list entries. I think Andrew suggested
lowering it to 1024. That I think may be too low, but I don't mind if it
is lowered somewhat from the current value.

Cheers,
Longman