From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934371AbbEOLnn (ORCPT ); Fri, 15 May 2015 07:43:43 -0400 Received: from mta-out1.inet.fi ([62.71.2.227]:52199 "EHLO johanna2.rokki.sonera.fi" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933731AbbEOLnl (ORCPT ); Fri, 15 May 2015 07:43:41 -0400 RazorGate-KAS: Rate: 5 RazorGate-KAS: {RECEIVED: dynamic ip detected} RazorGate-KAS: Envelope from: RazorGate-KAS: Version: 5.5.3 RazorGate-KAS: LuaCore: 80 2014-11-10_18-01-23 260f8afb9361da3c7edfd3a8e3a4ca908191ad29 RazorGate-KAS: Method: none RazorGate-KAS: Lua profiles 69136 [Nov 12 2014] RazorGate-KAS: Status: not_detected Date: Fri, 15 May 2015 14:43:14 +0300 From: "Kirill A. Shutemov" To: Vlastimil Babka Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Hugh Dickins , Dave Hansen , Mel Gorman , Rik van Riel , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , Sasha Levin , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv5 01/28] mm, proc: adjust PSS calculation Message-ID: <20150515114314.GF6250@node.dhcp.inet.fi> References: <1429823043-157133-1-git-send-email-kirill.shutemov@linux.intel.com> <1429823043-157133-2-git-send-email-kirill.shutemov@linux.intel.com> <5554AD4D.9040000@suse.cz> <20150515105621.GA6250@node.dhcp.inet.fi> <5555D98B.7010900@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5555D98B.7010900@suse.cz> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 15, 2015 at 01:33:31PM +0200, Vlastimil Babka wrote: > 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 > >>>Tested-by: Sasha Levin > >> > >>Acked-by: Vlastimil Babka > >> > >>(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? Kernel relies on dead-code elimination. You cannot build kernel with -O0. > 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... I think we could try to downgrade it BUG(). Although I found BUILD_BUG() useful few times. HPAGE_PMD_NR==1 would be just wrong. It would mean you can map order-0 page with PMD %-| -- Kirill A. Shutemov