Messages in this thread | | | Date | Fri, 20 Oct 2006 22:49:16 +0100 | From | Ralf Baechle <> | Subject | Re: [PATCH 1/3] Fix COW D-cache aliasing on fork |
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On Fri, Oct 20, 2006 at 01:10:59PM -0700, Linus Torvalds wrote:
> Ok, this sounds sane. > > What should we do about this? How does this patch look to people? > > (Totally untested, and I'm not sure we should even do that whole > "oldmm->mm_users" test, but I'm throwing it out here for discussion, in > case it matters for performance. The second D$ flush should obviously be > unnecessary for the common unthreaded case, which is why none of this has > mattered historically, I think). > > Comments? We need ARM, MIPS, sparc and S390 at the very least to sign off > on this, and somebody to write a nice explanation for the changelog (and > preferably do this through -mm too).
As a minimal solution your patch would work for MIPS but performance would be suboptimal.
With my D-cache alias series applied the flush_cache_mm() in dup_mmap() becomes entirely redundant. When I delete the call (not part of my patchset) it means 12% faster fork. But I'm not proposing this for 2.6.19.
Note this does not make the flush_cache_mm() on process termination redundant ...
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