Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934016AbbEOLSw (ORCPT ); Fri, 15 May 2015 07:18:52 -0400 Received: from mta-out1.inet.fi ([62.71.2.227]:40019 "EHLO kirsi1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754317AbbEOLSt (ORCPT ); Fri, 15 May 2015 07:18:49 -0400 Date: Fri, 15 May 2015 14:18:28 +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 03/28] memcg: adjust to support new THP refcounting Message-ID: <20150515111828.GC6250@node.dhcp.inet.fi> References: <1429823043-157133-1-git-send-email-kirill.shutemov@linux.intel.com> <1429823043-157133-4-git-send-email-kirill.shutemov@linux.intel.com> <5555A3D1.3010108@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5555A3D1.3010108@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 Content-Length: 1548 Lines: 35 On Fri, May 15, 2015 at 09:44:17AM +0200, Vlastimil Babka wrote: > On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote: > >As with rmap, with new refcounting we cannot rely on PageTransHuge() to > >check if we need to charge size of huge page form the cgroup. We need to > >get information from caller to know whether it was mapped with PMD or > >PTE. > > > >We do uncharge when last reference on the page gone. At that point if we > >see PageTransHuge() it means we need to unchange whole huge page. > > > >The tricky part is partial unmap -- when we try to unmap part of huge > >page. We don't do a special handing of this situation, meaning we don't > >uncharge the part of huge page unless last user is gone or > >split_huge_page() is triggered. In case of cgroup memory pressure > >happens the partial unmapped page will be split through shrinker. This > >should be good enough. > > > >Signed-off-by: Kirill A. Shutemov > >Tested-by: Sasha Levin > > Acked-by: Vlastimil Babka > > But same question about whether it should be using hpage_nr_pages() instead > of a constant. No. Compiler woundn't be able to optimize HPAGE_PMD_NR away for THP=n, since compound value cross compilation unit barrier. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/