From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI shortcircuit=no autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 334361F97E for ; Wed, 10 Oct 2018 13:59:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726827AbeJJVWM (ORCPT ); Wed, 10 Oct 2018 17:22:12 -0400 Received: from cloud.peff.net ([104.130.231.41]:35444 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1726515AbeJJVWM (ORCPT ); Wed, 10 Oct 2018 17:22:12 -0400 Received: (qmail 22743 invoked by uid 109); 10 Oct 2018 13:59:54 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Wed, 10 Oct 2018 13:59:54 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 17138 invoked by uid 111); 10 Oct 2018 13:59:02 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.94) with (ECDHE-RSA-AES256-GCM-SHA384 encrypted) SMTP; Wed, 10 Oct 2018 09:59:02 -0400 Authentication-Results: peff.net; auth=none Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Wed, 10 Oct 2018 09:59:52 -0400 Date: Wed, 10 Oct 2018 09:59:52 -0400 From: Jeff King To: SZEDER =?utf-8?B?R8OhYm9y?= Cc: Jacob Keller , Jacob Keller , Git mailing list Subject: Re: [PATCH v3] coccicheck: process every source file at once Message-ID: <20181010135952.GA2933@sigill.intra.peff.net> References: <20181002200710.15721-1-jacob.e.keller@intel.com> <20181005124048.GT23446@localhost> <20181005162517.GB11254@sigill.intra.peff.net> <20181005183904.GV23446@localhost> <20181005190216.GB17482@sigill.intra.peff.net> <20181005195413.GX23446@localhost> <20181009031542.GD6250@sigill.intra.peff.net> <20181010114441.GD23446@szeder.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181010114441.GD23446@szeder.dev> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Wed, Oct 10, 2018 at 01:44:41PM +0200, SZEDER Gábor wrote: > > So that's really weird and counter-intuitive, since we should be doing > > strictly less work. I know that spatch tries to parallelize itself, > > though from my tests, 1.0.4 does not. I wonder if the version in Travis > > differs in that respect and starts too many threads, and the extra time > > is going to contention and context switches. > > I don't think it does any parallel work. > > Here is the timing again from my previous email: > > 960.50user 22.59system 16:23.74elapsed 99%CPU (0avgtext+0avgdata 1606156maxresident)k > > Notice that 16:23 is 983s, and that it matches the sum of the user and > system times. I usually saw this kind of timing with CPU-intensive > single-threaded programs, and if there were any parallelization, then I > would expect the elapsed time to be at least somewhat smaller than the > other two. Ah, right, I should have been able to figure that out myself. So scratch that theory. My "hypervisor stalling our memory reads" theory is still plausible, but I don't know how we would test it. I guess in some sense it doesn't matter. If it's slower, we're not likely to be able to fix that. So I guess we just need the fallback to the current behavior. -Peff