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Subject: Re: [RFC PATCH 0/2] mm/vmstat: Reduce zone lock hold time when
 reading /proc/pagetypeinfo
To:     Michal Hocko <mhocko@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>
Cc:     Johannes Weiner <hannes@cmpxchg.org>, Roman Gushchin <guro@fb.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        Jann Horn <jannh@google.com>, Song Liu <songliubraving@fb.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Rafael Aquini <aquini@redhat.com>, linux-mm@kvack.org,
        LKML <linux-kernel@vger.kernel.org>
References: <20191023095607.GE3016@techsingularity.net>
 <20191023102737.32274-1-mhocko@kernel.org>
 <20191024082042.GS17610@dhcp22.suse.cz>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <55c08581-a9c8-27cc-9710-b2bfe1934c8e@redhat.com>
Date:   Thu, 24 Oct 2019 12:16:34 -0400
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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.c=
z
> 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