From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030309AbbEERvH (ORCPT ); Tue, 5 May 2015 13:51:07 -0400 Received: from mail-wg0-f52.google.com ([74.125.82.52]:35013 "EHLO mail-wg0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030279AbbEERvD (ORCPT ); Tue, 5 May 2015 13:51:03 -0400 Date: Tue, 5 May 2015 19:50:58 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Linux Kernel Mailing List , Andy Lutomirski , Borislav Petkov , Dave Hansen , Fenghua Yu , "H. Peter Anvin" , Oleg Nesterov , Thomas Gleixner Subject: Re: [PATCH 000/208] big x86 FPU code rewrite Message-ID: <20150505175058.GA27778@gmail.com> References: <1430843228-13749-1-git-send-email-mingo@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 * Linus Torvalds wrote: > On Tue, May 5, 2015 at 9:23 AM, Ingo Molnar wrote: > > 83 files changed, 3742 insertions(+), 2841 deletions(-) > > How much of this is just the added instrumentation? [...] Half of it is that, plus a lot of comments. > [...] Because that's almost a thousand new lines, which makes me > unhappy. The *last* thing we want is to make this thing bigger. > [...] So Boris suggested that I should move fpu/measure.c out of the FPU code anyway, which is fair enough, as it measures a lot of other low level details as well. Consider it done. With that taken out, the diffstat comes down to: 81 files changed, 3409 insertions(+), 3055 deletions(-) That's mostly 400 new lines of comments all around the FPU code, plus a bit of extra headers due to the split-up modules (50-100 lines maybe). > [...] I'm not convinced it's worth it adding some performance debug > code that doesn't really add any new information, and could be done > outside the kernel as just an independent module instead. Code size difference (with debugging off) on an x86-64 defconfig-ish kernel: text data bss filename 15030376 2574976 1634304 vmlinux.before 15023690 2578648 1634304 vmlinux.after The runtime size of the kernel got smaller by 7K. Considering that arch/x86/kernel/fpu/built-in.o is only 13K that's quite significant. Thanks, Ingo