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SubjectRe: SMP performance problem in 2.4 (was: Athlon spinlock performance)
Scott wrote:

>The problem is in `try_to_free_pages' and its associated routines,
>`shrink_caches' and `shrink_cache', in `mm/vmscan.c'. After I made some
>changes to greatly reduce lock contention in the slab allocator and
How did you change the slab locking?

> and then instrumented `shrink_cache' to see what it was
>doing, the problem showed up very clearly.
>In one approximately 60-second period with the problematic workload running,
>`try_to_free_pages' was called 511 times. It made 2597 calls to
>`shrink_caches', which made 2592 calls to `shrink_cache' (i.e. it was very
>rare for `kmem_cache_reap' to release enough pages itself).
2.6 contains a simple fix: I've removed kmem_cache_reap. Instead the
code checks for empty pages in the slab caches every other second.


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