linux-kernel - Re: [PATCH v1 0/5] stop anon reclaim when zram is full

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Date:	Tue, 2 Dec 2014 12:04:08 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Dan Streetman <ddstreet@...e.org>,
	Nitin Gupta <ngupta@...are.org>,
	Luigi Semenzato <semenzato@...gle.com>, juno.choi@....com
Subject: Re: [PATCH v1 0/5] stop anon reclaim when zram is full

Hello all,

On Mon, Sep 22, 2014 at 09:03:06AM +0900, Minchan Kim wrote:
> For zram-swap, there is size gap between virtual disksize
> and available physical memory size for zram so that VM
> can try to reclaim anonymous pages even though zram is full.
> It makes system alomost hang(ie, unresponsible) easily in
> my kernel build test(ie, 1G DRAM, CPU 12, 4G zram swap,
> 50M zram limit). VM should have killed someone.
> 
> This patch adds new hint SWAP_FULL so VM can ask fullness
> to zram and if it founds zram is full, VM doesn't reclaim
> anonymous pages until zram-swap gets new free space.
> 
> With this patch, I see OOM when zram-swap is full instead of
> hang with no response.
> 
> Minchan Kim (5):
>   zram: generalize swap_slot_free_notify
>   mm: add full variable in swap_info_struct
>   mm: VM can be aware of zram fullness
>   zram: add swap full hint
>   zram: add fullness knob to control swap full

I'm sorry for long delay for this patch althogh you guys gave great
feedback to me.

The reason I was hesitant about this patchset is that I want to avoid
weird fullness knob which was introduced by zsmalloc's internal limit.
So, before this feature, I hope we get zsmalloc's compaction firstly
Then, I hope to remove fullness knob totally.

Thanks.

> 
>  Documentation/ABI/testing/sysfs-block-zram |  10 +++
>  Documentation/filesystems/Locking          |   4 +-
>  drivers/block/zram/zram_drv.c              | 114 +++++++++++++++++++++++++++--
>  drivers/block/zram/zram_drv.h              |   2 +
>  include/linux/blkdev.h                     |   8 +-
>  include/linux/swap.h                       |   1 +
>  mm/page_io.c                               |   6 +-
>  mm/swapfile.c                              |  77 ++++++++++++++-----
>  8 files changed, 189 insertions(+), 33 deletions(-)
> 
> -- 
> 2.0.0
> 
> --
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-- 
Kind regards,
Minchan Kim
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