Messages in this thread |  | | Date | Wed, 3 Sep 2025 10:03:54 +0100 | | From | Kiryl Shutsemau <> | | Subject | Re: [PATCH 1/2] mm: Enable khugepaged to operate on non-writable VMAs |
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On Wed, Sep 03, 2025 at 11:16:34AM +0530, Dev Jain wrote: > Currently khugepaged does not collapse a region which does not have a > single writable page. This is wasteful since non-writable VMAs mapped by > the application won't benefit from THP collapse. Therefore, remove this > restriction and allow khugepaged to collapse a VMA with arbitrary > protections. > > Along with this, currently MADV_COLLAPSE does not perform a collapse on a > non-writable VMA, and this restriction is nowhere to be found on the > manpage - the restriction itself sounds wrong to me since the user knows > the protection of the memory it has mapped, so collapsing read-only > memory via madvise() should be a choice of the user which shouldn't > be overriden by the kernel. > > On an arm64 machine, an average of 5% improvement is seen on some mmtests > benchmarks, particularly hackbench, with a maximum improvement of 12%. > > Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Kiryl Shutsemau <kas@kernel.org>
-- Kiryl Shutsemau / Kirill A. Shutemov
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