linux-kernel - Re: [RFC 0/3] zram memory control enhance

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Date:	Wed, 06 Aug 2014 14:54:28 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org
CC:	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	juno.choi@....com, seungho1.park@....com,
	Luigi Semenzato <semenzato@...gle.com>,
	Nitin Gupta <ngupta@...are.org>
Subject: Re: [RFC 0/3] zram memory control enhance

On 08/05/2014 10:02 AM, Minchan Kim wrote:
> Notice! It's RFC. I didn't test at all but wanted to hear opinion
> during merge window when it's really busy time for Andrew so we could
> use the slack time to discuss without hurting him. ;-)
> 
> Patch 1 is to move pages_allocated in zsmalloc from size_class to zs_pool
> so zs_get_total_size_bytes of zsmalloc would be faster than old.
> zs_get_total_size_bytes could be used next patches frequently.
> 
> Patch 2 adds new feature which exports how many of bytes zsmalloc consumes
> during testing workload. Normally, before fixing the zram's disksize
> we have tested various workload and wanted to how many of bytes zram
> consumed.
> For it, we could poll mem_used_total of zram in userspace but the problem is
> when memory pressure is severe and heavy swap out happens suddenly then
> heavy swapin or exist while polling interval of user space is a few second,
> it could miss max memory size zram had consumed easily.
> With lack of information, user can set wrong disksize of zram so the result
> is OOM. So this patch adds max_mem_used for zram and zsmalloc supports it
> 
> Patch 3 is to limit zram memory consumption. Now, zram has no bound for
> memory usage so it could consume up all of system memory. It makes system
> memory control for platform hard so I have heard the feature several time.
> 
> Feedback is welcome!

Hi,

I haven't really reviewed the code yet, but I like the general idea. The
third patch in particular provides a very useful feature. I'm actually
surprised no one provided it earlier.

Jerome


> 
> Minchan Kim (3):
>   zsmalloc: move pages_allocated to zs_pool
>   zsmalloc/zram: add zs_get_max_size_bytes and use it in zram
>   zram: limit memory size for zram
> 
>  Documentation/blockdev/zram.txt |  2 ++
>  drivers/block/zram/zram_drv.c   | 58 +++++++++++++++++++++++++++++++++++++++++
>  drivers/block/zram/zram_drv.h   |  1 +
>  include/linux/zsmalloc.h        |  1 +
>  mm/zsmalloc.c                   | 50 +++++++++++++++++++++++++----------
>  5 files changed, 98 insertions(+), 14 deletions(-)
> 



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