linux-kernel - Re: [PATCH] z3fold: make pages

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Message-ID: <CAMJBoFMK_WH7q_y_=JgCJJ70YSSUhza1nQ0qVdurO6ZUT_kRLw@mail.gmail.com>
Date:   Fri, 4 Nov 2016 08:27:42 +0100
From:   Vitaly Wool <vitalywool@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Dan Streetman <ddstreet@...e.org>
Subject: Re: [PATCH] z3fold: make pages_nr atomic

On Thu, Nov 3, 2016 at 11:17 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 3 Nov 2016 22:24:07 +0100 Vitaly Wool <vitalywool@...il.com> wrote:
>
>> On Thu, Nov 3, 2016 at 10:14 PM, Andrew Morton
>> <akpm@...ux-foundation.org> wrote:
>> > On Thu, 3 Nov 2016 22:00:58 +0100 Vitaly Wool <vitalywool@...il.com> wrote:
>> >
>> >> This patch converts pages_nr per-pool counter to atomic64_t.
>> >
>> > Which is slower.
>> >
>> > Presumably there is a reason for making this change.  This reason
>> > should be described in the changelog.
>>
>> The reason [which I thought was somewhat obvious :) ] is that there
>> won't be a need to take a per-pool lock to read or modify that
>> counter.
>
> But the patch didn't change the locking.  And as far as I can tell,
> neither does "z3fold: extend compaction function".

Right. I'll come up with the locking rework shortly, but it will be a
RFC so I wanted to send it separately.

~vitaly