From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by kanga.kvack.org (Postfix) with ESMTP id F035F6B0038 for ; Thu, 5 Mar 2015 11:04:47 -0500 (EST) Received: by wibhm9 with SMTP id hm9so16367096wib.2 for ; Thu, 05 Mar 2015 08:04:47 -0800 (PST) Received: from jenni1.inet.fi (mta-out1.inet.fi. [62.71.2.203]) by mx.google.com with ESMTP id jz10si13429513wjc.98.2015.03.05.08.04.44 for ; Thu, 05 Mar 2015 08:04:44 -0800 (PST) Date: Thu, 5 Mar 2015 18:04:26 +0200 From: "Kirill A. Shutemov" Subject: Re: [PATCHv4 00/24] THP refcounting redesign Message-ID: <20150305160426.GA20370@node.dhcp.inet.fi> References: <1425486792-93161-1-git-send-email-kirill.shutemov@linux.intel.com> <54F85233.1010006@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54F85233.1010006@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Marchand Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Dave Hansen , Hugh Dickins , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, Mar 05, 2015 at 01:55:15PM +0100, Jerome Marchand wrote: > On 03/04/2015 05:32 PM, Kirill A. Shutemov wrote: > > Hello everybody, > > > > It's bug-fix update of my thp refcounting work. > > > > The goal of patchset is to make refcounting on THP pages cheaper with > > simpler semantics and allow the same THP compound page to be mapped with > > PMD and PTEs. This is required to get reasonable THP-pagecache > > implementation. > > > > With the new refcounting design it's much easier to protect against > > split_huge_page(): simple reference on a page will make you the deal. > > It makes gup_fast() implementation simpler and doesn't require > > special-case in futex code to handle tail THP pages. > > > > It should improve THP utilization over the system since splitting THP in > > one process doesn't necessary lead to splitting the page in all other > > processes have the page mapped. > > > [...] > > I believe all known bugs have been fixed, but I'm sure Sasha will bring more > > reports. > > > > The patchset also available on git: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git thp/refcounting/v4 > > > > Hi Kirill, > > I ran some ltp tests and it triggered two bugs: Okay. The root of both is change in page_mapped(). I'll think how to fix this. -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757454AbbCEQFJ (ORCPT ); Thu, 5 Mar 2015 11:05:09 -0500 Received: from mta-out1.inet.fi ([62.71.2.203]:44199 "EHLO jenni1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752743AbbCEQFG (ORCPT ); Thu, 5 Mar 2015 11:05:06 -0500 Date: Thu, 5 Mar 2015 18:04:26 +0200 From: "Kirill A. Shutemov" To: Jerome Marchand Cc: "Kirill A. Shutemov" , Andrew Morton , Andrea Arcangeli , Dave Hansen , Hugh Dickins , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv4 00/24] THP refcounting redesign Message-ID: <20150305160426.GA20370@node.dhcp.inet.fi> References: <1425486792-93161-1-git-send-email-kirill.shutemov@linux.intel.com> <54F85233.1010006@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54F85233.1010006@redhat.com> 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 Thu, Mar 05, 2015 at 01:55:15PM +0100, Jerome Marchand wrote: > On 03/04/2015 05:32 PM, Kirill A. Shutemov wrote: > > Hello everybody, > > > > It's bug-fix update of my thp refcounting work. > > > > The goal of patchset is to make refcounting on THP pages cheaper with > > simpler semantics and allow the same THP compound page to be mapped with > > PMD and PTEs. This is required to get reasonable THP-pagecache > > implementation. > > > > With the new refcounting design it's much easier to protect against > > split_huge_page(): simple reference on a page will make you the deal. > > It makes gup_fast() implementation simpler and doesn't require > > special-case in futex code to handle tail THP pages. > > > > It should improve THP utilization over the system since splitting THP in > > one process doesn't necessary lead to splitting the page in all other > > processes have the page mapped. > > > [...] > > I believe all known bugs have been fixed, but I'm sure Sasha will bring more > > reports. > > > > The patchset also available on git: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git thp/refcounting/v4 > > > > Hi Kirill, > > I ran some ltp tests and it triggered two bugs: Okay. The root of both is change in page_mapped(). I'll think how to fix this. -- Kirill A. Shutemov