linux-kernel - Re: [PATCH] z3fold: discourage use of pages that weren't compacted

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Date:   Tue, 15 Nov 2016 14:35:52 +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: discourage use of pages that weren't compacted

On Tue, Nov 15, 2016 at 1:33 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Fri, 11 Nov 2016 14:02:07 +0100 Vitaly Wool <vitalywool@...il.com> wrote:
>
>> If a z3fold page couldn't be compacted, we don't want it to be
>> used for next object allocation in the first place. It makes more
>> sense to add it to the end of the relevant unbuddied list. If that
>> page gets compacted later, it will be added to the beginning of
>> the list then.
>>
>> This simple idea gives 5-7% improvement in randrw fio tests and
>> about 10% improvement in fio sequential read/write.
>
> This patch appears to require "z3fold: use per-page spinlock", and
> "z3fold: use per-page spinlock" doesn't apply properly.
>
> So things are in a bit of a mess.

Yep, sorry about that.

> I presently have
>
> z3fold-limit-first_num-to-the-actual-range-of-possible-buddy-indexes.patch
> z3fold-make-pages_nr-atomic.patch
> z3fold-extend-compaction-function.patch

These are not interdependent.

> Please take a look, figure out what we should do.  Perhaps do it all as
> a coherent series rather than an interdependent dribble?

I'll come up with a 2-patch update in a short while.

~vitaly