From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753565AbaFJWOt (ORCPT ); Tue, 10 Jun 2014 18:14:49 -0400 Received: from mta-out1.inet.fi ([62.71.2.199]:46953 "EHLO kirsi1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255AbaFJWOs (ORCPT ); Tue, 10 Jun 2014 18:14:48 -0400 Date: Wed, 11 Jun 2014 01:14:31 +0300 From: "Kirill A. Shutemov" To: Andrea Arcangeli Cc: Christoph Lameter , "Kirill A. Shutemov" , Andrew Morton , Dave Hansen , Hugh Dickins , Mel Gorman , Rik van Riel , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH, RFC 00/10] THP refcounting redesign Message-ID: <20140610221431.GA10634@node.dhcp.inet.fi> References: <1402329861-7037-1-git-send-email-kirill.shutemov@linux.intel.com> <20140610204640.GA9594@node.dhcp.inet.fi> <20140610220451.GG19660@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140610220451.GG19660@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 11, 2014 at 12:04:51AM +0200, Andrea Arcangeli wrote: > On Tue, Jun 10, 2014 at 11:46:40PM +0300, Kirill A. Shutemov wrote: > > Agreed. The patchset drops tail page refcounting. > > Very possibly I misread something or a later patch fixes this up, I > just did a basic code review, but from the new code of split_huge_page > it looks like it returns -EBUSY after checking the individual tail > page refcounts, so it's not clear how that defines as "dropped". page_mapcount() here is really mapcount: how many times the page is mapped, not pins on tail pages as we have it now. > > + for (i = 0; i < HPAGE_PMD_NR; i++) > + tail_count += page_mapcount(page + i); > + if (tail_count != page_count(page) - 1) { > + BUG_ON(tail_count > page_count(page) - 1); > + compound_unlock(page); > + spin_unlock_irq(&zone->lru_lock); > + return -EBUSY; > -- > 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/ -- Kirill A. Shutemov From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f181.google.com (mail-we0-f181.google.com [74.125.82.181]) by kanga.kvack.org (Postfix) with ESMTP id 625BA6B010B for ; Tue, 10 Jun 2014 18:14:40 -0400 (EDT) Received: by mail-we0-f181.google.com with SMTP id q59so2949396wes.12 for ; Tue, 10 Jun 2014 15:14:39 -0700 (PDT) Received: from kirsi1.inet.fi (mta-out1.inet.fi. [62.71.2.199]) by mx.google.com with ESMTP id da1si18913342wib.71.2014.06.10.15.14.38 for ; Tue, 10 Jun 2014 15:14:39 -0700 (PDT) Date: Wed, 11 Jun 2014 01:14:31 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH, RFC 00/10] THP refcounting redesign Message-ID: <20140610221431.GA10634@node.dhcp.inet.fi> References: <1402329861-7037-1-git-send-email-kirill.shutemov@linux.intel.com> <20140610204640.GA9594@node.dhcp.inet.fi> <20140610220451.GG19660@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140610220451.GG19660@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: Christoph Lameter , "Kirill A. Shutemov" , Andrew Morton , Dave Hansen , Hugh Dickins , Mel Gorman , Rik van Riel , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, Jun 11, 2014 at 12:04:51AM +0200, Andrea Arcangeli wrote: > On Tue, Jun 10, 2014 at 11:46:40PM +0300, Kirill A. Shutemov wrote: > > Agreed. The patchset drops tail page refcounting. > > Very possibly I misread something or a later patch fixes this up, I > just did a basic code review, but from the new code of split_huge_page > it looks like it returns -EBUSY after checking the individual tail > page refcounts, so it's not clear how that defines as "dropped". page_mapcount() here is really mapcount: how many times the page is mapped, not pins on tail pages as we have it now. > > + for (i = 0; i < HPAGE_PMD_NR; i++) > + tail_count += page_mapcount(page + i); > + if (tail_count != page_count(page) - 1) { > + BUG_ON(tail_count > page_count(page) - 1); > + compound_unlock(page); > + spin_unlock_irq(&zone->lru_lock); > + return -EBUSY; > -- > 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/ -- Kirill A. Shutemov -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org