Messages in this thread | | | Date | Wed, 08 Dec 2004 14:50:07 -0800 | From | "Martin J. Bligh" <> | Subject | Re: Anticipatory prefaulting in the page fault handler V1 |
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> The page fault handler for anonymous pages can generate significant overhead > apart from its essential function which is to clear and setup a new page > table entry for a never accessed memory location. This overhead increases > significantly in an SMP environment. > > In the page table scalability patches, we addressed the issue by changing > the locking scheme so that multiple fault handlers are able to be processed > concurrently on multiple cpus. This patch attempts to aggregate multiple > page faults into a single one. It does that by noting > anonymous page faults generated in sequence by an application. > > If a fault occurred for page x and is then followed by page x+1 then it may > be reasonable to expect another page fault at x+2 in the future. If page > table entries for x+1 and x+2 would be prepared in the fault handling for > page x+1 then the overhead of taking a fault for x+2 is avoided. However > page x+2 may never be used and thus we may have increased the rss > of an application unnecessarily. The swapper will take care of removing > that page if memory should get tight.
I tried benchmarking it ... but processes just segfault all the time. Any chance you could try it out on SMP ia32 system?
M.
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