Re: [PATCH] slub: Avoid direct compaction if possible

[Christoph Lameter]

On Fri, 14 Jun 2013, Roman Gushchin wrote:

> But there is an actual problem, that this patch solves.
> Sometimes I saw the following issue on some machines:
> all CPUs are performing compaction, system time is about 80%,
> system is completely unreliable. It occurs only on machines
> with specific workload (distributed data storage system, so,
> intensive disk i/o is performed). A system can fall into
> this state fast and unexpectedly or by progressive degradation.

Well that is not a slab allocator specific issue but related to compaction
concurrency. Likely cache line contention is causing a severe slowday. But
that issue could be triggered by any subsystem that does lots of memory
allocations. I would suggest that we try to address the problem in the
compaction logic rather than modifying allocators.

Mel?
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