From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756639Ab3JGUQM (ORCPT ); Mon, 7 Oct 2013 16:16:12 -0400 Received: from mga03.intel.com ([143.182.124.21]:11728 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755801Ab3JGUQB (ORCPT ); Mon, 7 Oct 2013 16:16:01 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,1051,1371106800"; d="scan'208";a="371045976" From: Andi Kleen To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , David Ahern , Jiri Olsa Subject: Re: [RFC PATCH 00/50] tools/perf: Speed up the build system References: <1381147003-2574-1-git-send-email-mingo@kernel.org> Date: Mon, 07 Oct 2013 13:15:59 -0700 In-Reply-To: <1381147003-2574-1-git-send-email-mingo@kernel.org> (Ingo Molnar's message of "Mon, 7 Oct 2013 13:55:53 +0200") Message-ID: <87y564zvk0.fsf@tassilo.jf.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar writes: > > The series also includes a number of fixes and convenience features: > > - auto-detect the number of CPUs on the system and add the -j > option automatically FWIW I would prefer if you not do that automatically, because: - Often the optimal factor is not 1, but something like 1.5*CPUs (but I'm not sure it's the same on all systems, probably depends on the IO capacity and memory) - It may use a lot of memory, so should be something controlled by the user. - Often it's useful to use a few threads less to avoid interactivity problems on a workstation. - With LTO there can be rare cases where you need to lower it to avoid running out of memory. - Kernel build users should be already trained to set that parameter and it's not really a big burden. The rest looks like a great improvement. -Andi -- ak@linux.intel.com -- Speaking for myself only