Messages in this thread | | | Date | Fri, 15 May 2015 13:33:31 +0200 | From | Vlastimil Babka <> | Subject | Re: [PATCHv5 01/28] mm, proc: adjust PSS calculation |
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On 05/15/2015 12:56 PM, Kirill A. Shutemov wrote: > On Thu, May 14, 2015 at 04:12:29PM +0200, Vlastimil Babka wrote: >> On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote: >>> With new refcounting all subpages of the compound page are not nessessary >>> have the same mapcount. We need to take into account mapcount of every >>> sub-page. >>> >>> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> >>> Tested-by: Sasha Levin <sasha.levin@oracle.com> >> >> Acked-by: Vlastimil Babka <vbabka@suse.cz> >> >> (some nitpicks below) >> >>> --- >>> fs/proc/task_mmu.c | 43 ++++++++++++++++++++++--------------------- >>> 1 file changed, 22 insertions(+), 21 deletions(-) >>> >>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >>> index 956b75d61809..95bc384ee3f7 100644 >>> --- a/fs/proc/task_mmu.c >>> +++ b/fs/proc/task_mmu.c >>> @@ -449,9 +449,10 @@ struct mem_size_stats { >>> }; >>> >>> static void smaps_account(struct mem_size_stats *mss, struct page *page, >>> - unsigned long size, bool young, bool dirty) >>> + bool compound, bool young, bool dirty) >>> { >>> - int mapcount; >>> + int i, nr = compound ? hpage_nr_pages(page) : 1; >> >> Why not just HPAGE_PMD_NR instead of hpage_nr_pages(page)? > > Okay, makes sense. Compiler is smart enough to optimize away HPAGE_PMD_NR > for THP=n. (HPAGE_PMD_NR is BUILD_BUG() for THP=n)
Ah, BUILD_BUG()... I'm not sure we can rely on optimization to avoid BUILD_BUG(), what if somebody compiles with all optimizations off? So why not replace BUILD_BUG() with "1", or create a variant of HPAGE_PMD_NR that does that, for this case and patch 3. Seems better than testing PageTransHuge everywhere...
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