Messages in this thread | | | Date | Tue, 17 Aug 2004 08:51:25 -0700 | From | William Lee Irwin III <> | Subject | Re: page fault fastpath patch v2: fix race conditions, stats for 8,32 and 512 cpu SMP |
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On Tue, Aug 17, 2004 at 08:28:44AM -0700, Christoph Lameter wrote: > This is the second release of the page fault fastpath path. The fast path > avoids locking during the creation of page table entries for anonymous > memory in a threaded application running on a SMP system. The performance > increases significantly for more than 4 threads running concurrently. > Changes: > - Insure that it is safe to call the various functions without holding > the page_table_lock. > - Fix cases in rmap.c where a pte could be cleared for a very short time > before being set to another value by introducing a pte_xchg function. This > created a potential race condition with the fastpath code which checks for > a cleared pte without holding the page_table_lock. > - i386 support > - Various cleanups > Issue remaining: > - The fastpath increments mm->rss without acquiring the page_table_lock. > Introducing the page_table_lock even for a short time makes performance > drop to the level before the patch.
Hmm. I'm suspicious but I can't immediately poke a hole in it as it leaves most uses of ->page_table_lock in place. I can't help thinking there's a more comprehensive attack on the locking in this area, either.
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