Re: [Query] Performance degradation with memory compaction (on QC chip-set)

[Mel Gorman <mgorman@suse.de>]

On Sun, May 12, 2013 at 08:00:26PM -0700, PINTU KUMAR wrote:
> Dear Mel Gorman,
> 
> I have one question about memory compaction.
> Kernel version: kernel-3.4 (ARM)
> Chipset: Qual-Comm MSM8930 dual-core.
> 
> We wanted to enable CONFIG_COMPACTION for our product with kernel-3.4.
> But QC commented that, enabling compaction on their chip-set is causing performance degradation for some streaming scenarios (from the beginning).
> 
> I wanted to know is this possible always?
> We used compaction with exynos processor and did not observe any performance degradation.
> 

I suspect one of their drivers are using high-order allocations and
hitting compaction as a result. Compaction is not guaranteed to cause
overhead but if it's in use then the scanning and copying overhead can
cause problems.

> Please let me know your comments.
> It will be helpful to decide on enabling compaction or not.
> 

Depends on workload and drivers.

-- 
Mel Gorman
SUSE Labs

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