From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755563Ab3JHItm (ORCPT ); Tue, 8 Oct 2013 04:49:42 -0400 Received: from mga14.intel.com ([143.182.124.37]:18047 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754698Ab3JHIth (ORCPT ); Tue, 8 Oct 2013 04:49:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,1056,1371106800"; d="scan'208";a="371299664" From: "Kirill A. Shutemov" To: Andrew Morton , Peter Zijlstra Cc: "Kirill A. Shutemov" , Alex Thorlton , Ingo Molnar , Naoya Horiguchi , "Eric W . Biederman" , "Paul E . McKenney" , Al Viro , Andi Kleen , Andrea Arcangeli , Dave Hansen , Dave Jones , David Howells , Frederic Weisbecker , Johannes Weiner , Kees Cook , Mel Gorman , Michael Kerrisk , Oleg Nesterov , Rik van Riel , Robin Holt , Sedat Dilek , Srikar Dronamraju , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org In-Reply-To: <20131007160907.3a4aca3e7eae404767ed3a8e@linux-foundation.org> References: <1381154053-4848-1-git-send-email-kirill.shutemov@linux.intel.com> <20131007160907.3a4aca3e7eae404767ed3a8e@linux-foundation.org> Subject: Re: [PATCHv5 00/11] split page table lock for PMD tables Content-Transfer-Encoding: 7bit Message-Id: <20131008084927.BC193E0090@blue.fi.intel.com> Date: Tue, 8 Oct 2013 11:49:27 +0300 (EEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > On Mon, 7 Oct 2013 16:54:02 +0300 "Kirill A. Shutemov" wrote: > > > Alex Thorlton noticed that some massively threaded workloads work poorly, > > if THP enabled. This patchset fixes this by introducing split page table > > lock for PMD tables. hugetlbfs is not covered yet. > > > > This patchset is based on work by Naoya Horiguchi. > > I think I'll summarise the results thusly: > > : THP off, v3.12-rc2: 18.059261877 seconds time elapsed > : THP off, patched: 16.768027318 seconds time elapsed > : > : THP on, v3.12-rc2: 42.162306788 seconds time elapsed > : THP on, patched: 8.397885779 seconds time elapsed > : > : HUGETLB, v3.12-rc2: 47.574936948 seconds time elapsed > : HUGETLB, patched: 19.447481153 seconds time elapsed > > What sort of machines are we talking about here? Can mortals expect to > see such results on their hardware, or is this mainly on SGI nuttyware? I've tested on 4 socket Westmere: 40 cores / 80 threads. With 4 threads, I can see 8% improvement on THP. Nothing comparing to 36 times on Alex's 512 cores, but still... > I'm seeing very few reviewed-by's and acked-by's in here, which is a > bit surprising and disappointing for a large patchset at v5. Are you > sure none were missed? Peter looked through, but I haven't got any tags from him. > The new code is enabled only for x86. Why is this? x86 is the only hardware I have to test. > What must arch maintainers do to enable it? Have you any particular > suggestions, warnings etc to make their lives easier? The last patch is a good illustration what need to be done. It's very straight forward, I don't see any pitfalls. > I assume the patchset won't damage bisectability? If our bisecter has > only the first eight patches applied, the fact that > CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK cannot be enabled protects from > failures? Unless CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK defined, pmd_lockptr() will return mm->page_table_lock: we can convert code to new api stet-by-step without breaking anything. -- Kirill A. Shutemov