linux-kernel - Re: [PATCH v2] zram: Prevent page allocation failure during zcomp_strm

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Message-ID: <20151121021542.GB3121@swordfish>
Date:	Sat, 21 Nov 2015 11:15:43 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Kyeongdon Kim <kyeongdon.kim@....com>
Cc:	minchan@...nel.org, akpm@...ux-foundation.org, ngupta@...are.org,
	linux-kernel@...r.kernel.org, sergey.senozhatsky@...il.com,
	sergey.senozhatsky.work@...il.com
Subject: Re: [PATCH v2] zram: Prevent page allocation failure during
 zcomp_strm_alloc

On (11/21/15 11:10), Sergey Senozhatsky wrote:
> Cc Andrew
> 
> On (11/20/15 19:02), Kyeongdon Kim wrote:
> > When we're using LZ4 multi compression streams for zram swap,
> > we found out page allocation failure message in system running test.
> > That was not only once, but a few(2 - 5 times per test).
> > Also, some failure cases were continually occurring to try allocation
> > order 3.
> > 
> > In order to make parallel compression private data, we should call
> > kzalloc() with order 2/3 in runtime(lzo/lz4). But if there is no order
> >  2/3 size memory in that time, page allocation fails.
> > This patch makes to use vmalloc() as fallback of kmalloc(), this
> > prevents page alloc failure warning.
> > 
> > After this, we never found warning message in running test, also
> > It could reduce process startup latency about 60-120ms in each case.
> 
> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> 

with the only nit that the subject should be "try kmalloc() before vmalloc()"
or similar, not "prevent page allocation failure", I think.

	-ss
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