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authorRobin Holt <holt@sgi.com>2010-04-23 10:36:22 -0500
committerH. Peter Anvin <hpa@zytor.com>2010-04-23 15:57:23 -0700
commit1f9cc3cb6a27521edfe0a21abf97d2bb11c4d237 (patch)
treec9af6a71398aed690c1fa813498a0aed8abf2d7b /lib
parent4daa2a8093ecd1148270a1fc64e99f072b8c2901 (diff)
x86, pat: Update the page flags for memtype atomically instead of using memtype_lock
While testing an application using the xpmem (out of kernel) driver, we noticed a significant page fault rate reduction of x86_64 with respect to ia64. For one test running with 32 cpus, one thread per cpu, it took 01:08 for each of the threads to vm_insert_pfn 2GB worth of pages. For the same test running on 256 cpus, one thread per cpu, it took 14:48 to vm_insert_pfn 2 GB worth of pages. The slowdown was tracked to lookup_memtype which acquires the spinlock memtype_lock. This heavily contended lock was slowing down vm_insert_pfn(). With the cmpxchg on page->flags method, both the 32 cpu and 256 cpu cases take approx 00:01.3 seconds to complete. Signed-off-by: Robin Holt <holt@sgi.com> LKML-Reference: <20100423153627.751194346@gulag1.americas.sgi.com> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@gmail.com> Cc: Rafael Wysocki <rjw@novell.com> Reviewed-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'lib')
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