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

Vlastimil Babka
2015-09-14T14:14:29Z

On 09/14/2015 04:12 PM, Vitaly Wool wrote:
> On Mon, Sep 14, 2015 at 4:01 PM, Vlastimil Babka <vbabka@suse.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
>