linux-kernel - Re: [RFC][PATCHv2 0/8] introduce automatic pool compaction

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Message-ID: <20150610000755.GB596@swordfish>
Date:	Wed, 10 Jun 2015 09:07:55 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCHv2 0/8] introduce automatic pool compaction

Hello,

On (06/10/15 09:04), Minchan Kim wrote:
> Hello Sergey,
> 
> Thanks for looking this and sorry for the delay for review.
> I don't have a time to hold a review yet.
> Please wait and I try to get a time within this week.
> 
> Thanks for your patience.

sure, no problem at all.

	-ss

> On Fri, Jun 05, 2015 at 09:03:50PM +0900, Sergey Senozhatsky wrote:
> > Hello,
> > 
> > This patch set tweaks compaction and makes it possible to trigger
> > pool compaction automatically when system is getting low on memory.
> > 
> > zsmalloc in some cases can suffer from a notable fragmentation and
> > compaction can release some considerable amount of memory. The problem
> > here is that currently we fully rely on user space to perform compaction
> > when needed. However, performing zsmalloc compaction is not always an
> > obvious thing to do. For example, suppose we have a `idle' fragmented
> > (compaction was never performed) zram device and system is getting low
> > on memory due to some 3rd party user processes (gcc LTO, or firefox, etc.).
> > It's quite unlikely that user space will issue zpool compaction in this
> > case. Besides, user space cannot tell for sure how badly pool is
> > fragmented; however, this info is known to zsmalloc and, hence, to a
> > shrinker.
> > 
> > v2:
> > -- use a slab shrinker instead of triggering compaction from zs_free (Minchan)
> > 
> > Sergey Senozhatsky (8):
> >   zsmalloc: drop unused variable `nr_to_migrate'
> >   zsmalloc: partial page ordering within a fullness_list
> >   zsmalloc: lower ZS_ALMOST_FULL waterline
> >   zsmalloc: always keep per-class stats
> >   zsmalloc: introduce zs_can_compact() function
> >   zsmalloc: cosmetic compaction code adjustments
> >   zsmalloc/zram: move `num_migrated' to zs_pool
> >   zsmalloc: register a shrinker to trigger auto-compaction
> > 
> >  drivers/block/zram/zram_drv.c |  12 +--
> >  drivers/block/zram/zram_drv.h |   1 -
> >  include/linux/zsmalloc.h      |   1 +
> >  mm/zsmalloc.c                 | 228 +++++++++++++++++++++++++++---------------
> >  4 files changed, 152 insertions(+), 90 deletions(-)
> > 
> > -- 
> > 2.4.2.387.gf86f31a
> > 
> 
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