On Tue, Oct 02, 2012 at 06:19:22PM +0300, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
>
> 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 <aarcange@xxxxxxxxxx>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>