| Date | Wed, 4 Sep 2013 17:44:30 +0900 | From | Joonsoo Kim <> | Subject | Re: [PATCH v2 19/20] mm, hugetlb: retry if failed to allocate and there is concurrent user |
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On Fri, Aug 09, 2013 at 06:26:37PM +0900, Joonsoo Kim wrote: > If parallel fault occur, we can fail to allocate a hugepage, > because many threads dequeue a hugepage to handle a fault of same address. > This makes reserved pool shortage just for a little while and this cause > faulting thread who can get hugepages to get a SIGBUS signal. > > To solve this problem, we already have a nice solution, that is, > a hugetlb_instantiation_mutex. This blocks other threads to dive into > a fault handler. This solve the problem clearly, but it introduce > performance degradation, because it serialize all fault handling. > > Now, I try to remove a hugetlb_instantiation_mutex to get rid of > performance degradation. For achieving it, at first, we should ensure that > no one get a SIGBUS if there are enough hugepages. > > For this purpose, if we fail to allocate a new hugepage when there is > concurrent user, we return just 0, instead of VM_FAULT_SIGBUS. With this, > these threads defer to get a SIGBUS signal until there is no > concurrent user, and so, we can ensure that no one get a SIGBUS if there > are enough hugepages. > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> >
Hello, David. May I ask to you to review this one? I guess that you already thought about the various race condition, so I think that you are the most appropriate reviewer to this patch. :)
Thanks.
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