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

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Message-Id: <20161114163326.b5e991b77745bed6db221bfe@linux-foundation.org>
Date:   Mon, 14 Nov 2016 16:33:26 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Vitaly Wool <vitalywool@...il.com>
Cc:     Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org,
        Dan Streetman <ddstreet@...e.org>
Subject: Re: [PATCH] z3fold: discourage use of pages that weren't compacted

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.

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

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