Re: missing madvise functionality

Ulrich Drepper
2007-04-05T06:19:42Z

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Eric Dumazet wrote:
> Database workload, where the user multi threaded app is constantly
> accessing GBytes of data, so L2 cache hit is very small. If you want to
> oprofile it, with say a CPU_CLK_UNHALTED:5000 event, then find_vma() is
> in the top 5.

We did have a workload with lots of Java and databases at some point
when many VMAs were the issue. I brought this up here one, maybe two
years ago and I think Blaisorblade went on and looked into avoiding VMA
splits by having mprotect() not split VMAs and instead store the flags
in the page table somewhere. I don't remember the details.

Nothing came out of this but if this is possible it would be yet another
way to avoid mmap_sem locking, right?

--
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖

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