linux-kernel - Re: [PATCH 0/3] allow zram to use zbud as underlying allocator

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Message-ID: <55F6D641.6010209@suse.cz>
Date:	Mon, 14 Sep 2015 16:14:25 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Vitaly Wool <vitalywool@...il.com>
Cc:	minchan@...nel.org, sergey.senozhatsky@...il.com,
	ddstreet@...e.org, LKML <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org
Subject: Re: [PATCH 0/3] allow zram to use zbud as underlying allocator

On 09/14/2015 04:12 PM, Vitaly Wool wrote:
> On Mon, Sep 14, 2015 at 4:01 PM, Vlastimil Babka <vbabka@...e.cz> wrote:
>>
>> On 09/14/2015 03:49 PM, Vitaly Wool wrote:
>>>
>>> While using ZRAM on a small RAM footprint devices, together with
>>> KSM,
>>> I ran into several occasions when moving pages from compressed swap back
>>> into the "normal" part of RAM caused significant latencies in system
>>
>>
>> I'm sure Minchan will want to hear the details of that :)
>>
>>> operation. By using zbud I lose in compression ratio but gain in
>>> determinism, lower latencies and lower fragmentation, so in the coming
>>
>>
>> I doubt the "lower fragmentation" part given what I've read about the design of zbud and zsmalloc?
>
> As it turns out, I see more cases of compaction kicking in and
> significantly more compact_stalls with zsmalloc.

Interesting, I thought that zsmalloc doesn't need contiguous high-order 
pages.

> ~vitaly
>

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