On 03/10/2011 09:04 PM, Andrea Arcangeli wrote:
Hello everyone, I've been wondering why mremap is sending one IPI for each page that it moves. I tried to remove that so we send an IPI for each vma/syscall (not for each pte/page). I also added native THP support without calling split_huge_page unconditionally if both the source and destination alignment allows a pmd_trans_huge to be preserved (the mremap extension and truncation already preserved existing hugepages but the move into new place didn't yet). If the destination alignment isn't ok, split_huge_page is unavoidable but that is an userland/hardware limitation, not really something we can optimize further in the kernel. I've no real numbers yet (volanomark results are mostly unchanged, it's a tinybit faster but it may be measurement error, and it doesn't seem to call mremap enough, but the thp_split number in /proc/vmstat seem to go down close to zero, maybe other JIT workloads will benefit?).
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