Messages in this thread | | | Date | Mon, 13 Feb 2006 11:54:21 +0100 | From | Ingo Molnar <> | Subject | Re: calibrate_migration_costs takes ages on s390 |
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* David S. Miller <davem@davemloft.net> wrote:
> Things are not as slow, but definitely slow on sparc64 too, and it's > also due to the migration cost calculations. > > It's also really bad that it's using vmalloc(), for one thing, because > this thrashes the TLB (some of us have 64-entry software replaced > TLBs) and also because you can make no guarentees about how well the > backing physical pages will distribute into the L2 cache.
the TLB trashing is intended, to calculate the worst-case migration cost. If userspace is TLB-intensive, it will trash TLBs just as much.
> As a result, wildly different run-to-run results can be expected > particularly for systems with 1-way or 2-way set assosciative L2 > caches, which are common on sparc64. I don't know about s390.
s390 is clearly a special-base, being a virtual platform. But the calibration should be improved to work better on sparc64.
Do things get better if you fill out include/asm-sparc64/system.h's sched_cacheflush() function, to flush the L2 cache? That should at least make the cache state more or less reproducable across runs.
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