Re: [PATCH] z3fold: make pages_nr atomic

[Vitaly Wool]

On Thu, Nov 3, 2016 at 11:17 PM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 3 Nov 2016 22:24:07 +0100 Vitaly Wool <vitalywool@xxxxxxxxx> wrote:
>
>> On Thu, Nov 3, 2016 at 10:14 PM, Andrew Morton
>> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>> > On Thu, 3 Nov 2016 22:00:58 +0100 Vitaly Wool <vitalywool@xxxxxxxxx> 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