Messages in this thread | | | Date | Thu, 29 Aug 2002 16:06:22 -0700 | From | William Lee Irwin III <> | Subject | Re: [PATCH] low-latency zap_page_range() |
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On Thu, Aug 29, 2002 at 10:37:02PM +0000, Linus Torvalds wrote: > You will NOT. > The page_table_lock protects against page stealing of the VM and > concurrent page-faults, nothing else. There is no way you can get > contention on it under any reasonable load that doesn't involve heavy > out-of-memory behaviour, simply because > - the lock is per-mm > - all "regular" paths that care about this also get the mmap semaphore > In short, that spinlock has _zero_ scalability impact. You can > theoretically get contention on it without memory pressure only by > having hundreds of threads page-faulting at the same time (getting a > read-lock on the mmap semaphore), but by then your performance has > nothing to do with the spinlock, and everything to do with the page > faults themselves. > (In fact, I can almost guarantee that most of the long hold-times are > for exit(), not for munmap(). And in that case the spinlock cannot get > any non-pagestealer contention at all, since nobody else is using the > MM)
All I have to go on is a report this has happened and a low-priority task to investigate it at some point in the future. I'll send you data either demonstrating it or exonerating it when I eventually get to it.
Cheers, Bill - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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