Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932754AbaGWSFK (ORCPT ); Wed, 23 Jul 2014 14:05:10 -0400 Received: from asavdk3.altibox.net ([109.247.116.14]:56963 "EHLO asavdk3.altibox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932561AbaGWSFI (ORCPT ); Wed, 23 Jul 2014 14:05:08 -0400 Date: Wed, 23 Jul 2014 20:05:01 +0200 From: Sam Ravnborg To: Andi Kleen Cc: Andi Kleen , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Dirk Gouders , mmarek@suse.cz Subject: Re: [PATCH 1/2] kbuild: Support split debug info v3 Message-ID: <20140723180501.GA15749@ravnborg.org> References: <1405466172-17055-1-git-send-email-andi@firstfloor.org> <20140720190420.GA4630@ravnborg.org> <20140720211901.GQ5803@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140720211901.GQ5803@tassilo.jf.intel.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 20, 2014 at 02:19:01PM -0700, Andi Kleen wrote: > > Why are as only called with -Wa,-gdwarf-2 in the non-split case? > > Is this a bug or intentional? > > If it is intentional then it is not explained. > > Probably was a merging mistake. Will fix. > > > > + help > > > + Generate debug info into separate .dwo files. This can be > > > + faster for building than including the debug information directly > > Here the "faster" part is promoted. > > But in your cover letter you actually highlight the "smaller" case > > as more significant. > > Maybe include info on both positive items. > > I currently don't see it significantly faster in my setup, will > mention size. It may be in others though. Feel free to test. I tried to test this on my setup - it is a Intel Atom with 2 cores. 16 GB RAM, a 7200 RPM stat disk. In other words a low-spec setup. Base config was "make allnoconfig" make KCFLAGS=-g real 3m35.967s user 12m19.270s sys 1m15.082s make KCFLAGS=-gsplit-dwarf real 3m33.366s user 12m11.156s sys 1m17.772s I did like this: echo time make -j4 -s KCFLAGS=-gsplit-dwarf time make -j4 -s KCFLAGS=-gsplit-dwarf echo time make -j4 -s KCFLAGS=-g time make -j4 -s KCFLAGS=-g echo time make -j4 -s KCFLAGS=-gsplit-dwarf time make -j4 -s KCFLAGS=-gsplit-dwarf echo time make -j4 -s KCFLAGS=-g time make -j4 -s KCFLAGS=-g echo time make -j4 -s KCFLAGS=-gsplit-dwarf time make -j4 -s KCFLAGS=-gsplit-dwarf echo time make -j4 -s KCFLAGS=-g time make -j4 -s KCFLAGS=-g The figures are from last run - but the other runs had compareable times. So in short I see a ~3 seconds speedup - out of 210 seconds. Thats less than I anticipated. But a speed-up never the less - which was consistent over all three runs. Sam -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/