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

Vitaly Wool
2015-09-30T15:46:30Z

On Wed, Sep 30, 2015 at 5:37 PM, Vlastimil Babka <vbabka@suse.cz> wrote:
> On 09/25/2015 11:54 AM, Vitaly Wool wrote:
>>
>> Hello Minchan,
>>
>> the main use case where I see unacceptably long stalls in UI with
>> zsmalloc is switching between users in Android.
>> There is a way to automate user creation and switching between them so
>> the test I run both to get vmstat statistics and to profile stalls is
>> to create a user, switch to it and switch back. Each test cycle does
>> that 10 times, and all the results presented below are averages for 20
>> runs.
>>
>> Kernel configurations used for testing:
>>
>> (1): vanilla
>> (2): (1) plus "make SLUB atomic" patch [1]
>> (3): (1) with zbud instead of zsmalloc
>> (4): (2) with compaction defer logic mostly disabled
>
>
> Disabling compaction deferring leads to less compaction stalls? That indeed
> looks very weird and counter-intuitive. Also what's "mostly" disabled mean?

Not that I'm not surprised myself. However, this is how it goes.
Namely, I reverted the following patches:
- mm, compaction: defer each zone individually instead of preferred zone
- mm, compaction: embed migration mode in compact_control
- mm, compaction: add per-zone migration pfn cache for async compaction
- ￼mm: compaction: encapsulate defer reset logic

~vitaly