On Tue, Oct 02, 2012 at 06:19:22PM +0300, Kirill A. Shutemov wrote: > From: "Kirill A. Shutemov" <[email protected]> > > During testing I noticed big (up to 2.5 times) memory consumption overhead > on some workloads (e.g. ft.A from NPB) if THP is enabled. > > The main reason for that big difference is lacking zero page in THP case. > We have to allocate a real page on read page fault. > > A program to demonstrate the issue: > #include <assert.h> > #include <stdlib.h> > #include <unistd.h> > > #define MB 1024*1024 > > int main(int argc, char **argv) > { > char *p; > int i; > > posix_memalign((void **)&p, 2 * MB, 200 * MB); > for (i = 0; i < 200 * MB; i+= 4096) > assert(p[i] == 0); > pause(); > return 0; > } > > With thp-never RSS is about 400k, but with thp-always it's 200M. > After the patcheset thp-always RSS is 400k too. > > v3: > - fix potential deadlock in refcounting code on preemptive kernel. > - do not mark huge zero page as movable. > - fix typo in comment. > - Reviewed-by tag from Andrea Arcangeli. > v2: > - Avoid find_vma() if we've already had vma on stack. > Suggested by Andrea Arcangeli. > - Implement refcounting for huge zero page. > > Kirill A. Shutemov (10): > thp: huge zero page: basic preparation > thp: zap_huge_pmd(): zap huge zero pmd > thp: copy_huge_pmd(): copy huge zero page > thp: do_huge_pmd_wp_page(): handle huge zero page > thp: change_huge_pmd(): keep huge zero page write-protected > thp: change split_huge_page_pmd() interface > thp: implement splitting pmd for huge zero page > thp: setup huge zero page on non-write page fault > thp: lazy huge zero page allocation > thp: implement refcounting for huge zero page
Reviewed-by: Andrea Arcangeli <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
