From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753512Ab3ACRJn (ORCPT ); Thu, 3 Jan 2013 12:09:43 -0500 Received: from mail-la0-f49.google.com ([209.85.215.49]:63723 "EHLO mail-la0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753423Ab3ACRJm (ORCPT ); Thu, 3 Jan 2013 12:09:42 -0500 Message-ID: <1357232977.1886.17.camel@mesosphere.localdomain> Subject: Re: mmap() scalability in the presence of the MAP_POPULATE flag From: Roman Dubtsov To: Michel Lespinasse Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Rik van Riel , Andrew Morton , Hugh Dickins Date: Fri, 04 Jan 2013 00:09:37 +0700 In-Reply-To: References: <1357145418.5429.17.camel@mesosphere.localdomain> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.2 (3.6.2-3.fc18) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2013-01-02 at 16:09 -0800, Michel Lespinasse wrote: > > Is there an interest in fixing this or concurrent mmaps() from the same > > process are too much of a corner case to worry about it? > > Funny this comes up again. I actually have a patch series that is > supposed to do that: > [PATCH 0/9] Avoid populating unbounded num of ptes with mmap_sem held > > However, the patches are still pending, didn't get much review > (probably not enough for Andrew to take them at this point), and I > think everyone forgot about them during the winter break. > > Care to have a look at that thread and see if it works for you ? > > (caveat: you will possibly also need "[PATCH 10/9] mm: make > do_mmap_pgoff return populate as a size in bytes, not as a bool" to > make the series actually work for you) I applied the patches on top of 3.7.1. Here're the results for 4 threads concurrently mmap()-ing 10 64MB buffers in a loop without munmap()-s. The data is from a Nehalem i7-920 single-socket 4-core CPU. I've also added the older data I have for the 3.6.11 (patched and not) for reference. 3.6.11 vanilla, do not populate: 0.001 seconds 3.6.11 vanilla, populate via a loop: 0.216 seconds 3.6.11 vanilla, populate via MAP_POPULATE: 0.358 seconds 3.6.11 + crude patch, do not populate: 0.002 seconds 3.6.11 + crude patch, populate via loop: 0.215 seconds 3.6.11 + crude patch, populate via MAP_POPULATE: 0.217 seconds 3.7.1 vanilla, do not populate: 0.001 seconds 3.7.1 vanilla, populate via a loop: 0.216 seconds 3.7.1 vanilla, populate via MAP_POPULATE: 0.411 seconds 3.7.1 + patch series, do not populate: 0.001 seconds 3.7.1 + patch series, populate via loop: 0.216 seconds 3.7.1 + patch series, populate via MAP_POPULATE: 0.273 seconds So, the patch series mentioned above do improve performance but as far as I can read the benchmarking data there's still some performance left on the table. Regards, Roma