From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3BA83C4346E for ; Sun, 27 Sep 2020 21:03:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00FB92311C for ; Sun, 27 Sep 2020 21:03:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726314AbgI0VDB (ORCPT ); Sun, 27 Sep 2020 17:03:01 -0400 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:55548 "EHLO mail2-relais-roc.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726267AbgI0VDB (ORCPT ); Sun, 27 Sep 2020 17:03:01 -0400 X-IronPort-AV: E=Sophos;i="5.77,311,1596492000"; d="scan'208";a="469746023" Received: from abo-173-121-68.mrs.modulonet.fr (HELO hadrien) ([85.68.121.173]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Sep 2020 22:55:53 +0200 Date: Sun, 27 Sep 2020 22:55:52 +0200 (CEST) From: Julia Lawall X-X-Sender: jll@hadrien To: Sumera Priyadarsini cc: corbet@lwn.net, michal.lkml@markovi.net, Gilles.Muller@lip6.fr, linux-doc@vger.kernel.org, nicolas.palix@imag.fr, linux-kernel@vger.kernel.org, cocci@systeme.lip6.fr Subject: Re: [Cocci] [PATCH 1/2] scripts: coccicheck: Change default value for parallelism In-Reply-To: <3beb97122995eafe3f0b831e36167b1edadb47c5.1600945451.git.sylphrenadin@gmail.com> Message-ID: References: <3beb97122995eafe3f0b831e36167b1edadb47c5.1600945451.git.sylphrenadin@gmail.com> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, 24 Sep 2020, Sumera Priyadarsini wrote: > By default, coccicheck utilizes all available threads to implement > parallelisation. However, when all available threads are used, > a decrease in performance is noted. The elapsed time is minimum > when at most one thread per core is used. > > For example, on benchmarking the semantic patch kfree.cocci for > usb/serial using hyperfine, the outputs obtained for J=5 and J=2 > are 1.32 and 1.90 times faster than those for J=10 and J=9 > respectively for two separate runs. For the larger drivers/staging > directory, minimium elapsed time is obtained for J=3 which is 1.86 > times faster than that for J=12. The optimal J value does not > exceed 6 in any of the test runs. The benchmarks are run on a machine > with 6 cores, with 2 threads per core, i.e, 12 hyperthreads in all. > > To improve performance, modify coccicheck to use at most only > one thread per core by default. > > Signed-off-by: Sumera Priyadarsini I have applied this one, so just the patch on the docuemtnation needs to be improved. julia > > --- > Changes in V2: > - Change commit message as suggested by Julia Lawall > Changes in V3: > - Use J/2 as optimal value for machines with more > than 8 hyperthreads as well. > --- > scripts/coccicheck | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/scripts/coccicheck b/scripts/coccicheck > index e04d328210ac..a72aa6c037ff 100755 > --- a/scripts/coccicheck > +++ b/scripts/coccicheck > @@ -75,8 +75,13 @@ else > OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE" > fi > > + # Use only one thread per core by default if hyperthreading is enabled > + THREADS_PER_CORE=$(lscpu | grep "Thread(s) per core: " | tr -cd [:digit:]) > if [ -z "$J" ]; then > NPROC=$(getconf _NPROCESSORS_ONLN) > + if [ $THREADS_PER_CORE -gt 1 -a $NPROC -gt 2 ] ; then > + NPROC=$((NPROC/2)) > + fi > else > NPROC="$J" > fi > -- > 2.25.1 > > _______________________________________________ > Cocci mailing list > Cocci@systeme.lip6.fr > https://systeme.lip6.fr/mailman/listinfo/cocci >