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

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Message-ID: <CALZtONDBviZ7HWyeERqG8-=5FLJCx8uMKKTj+5OHmKZ3-QX55w@mail.gmail.com>
Date:   Fri, 25 Nov 2016 09:33:47 -0500
From:   Dan Streetman <ddstreet@...e.org>
To:     Vitaly Wool <vitalywool@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] z3fold: make pages_nr atomic

On Fri, Nov 4, 2016 at 3:27 AM, Vitaly Wool <vitalywool@...il.com> wrote:
> 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.

this is still in mmotm, and it seems the later patches rely on it, so
while i agree that the changelog should be clearer about why it's
needed, the change itself looks ok.

Acked-by: Dan Streetman <ddstreet@...e.org>

>
> ~vitaly