Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752235AbbBUSfB (ORCPT ); Sat, 21 Feb 2015 13:35:01 -0500 Received: from mail-wi0-f181.google.com ([209.85.212.181]:58938 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751997AbbBUSe7 (ORCPT ); Sat, 21 Feb 2015 13:34:59 -0500 Date: Sat, 21 Feb 2015 19:34:55 +0100 From: Ingo Molnar To: Borislav Petkov Cc: Andy Lutomirski , Oleg Nesterov , Rik van Riel , x86@kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs Message-ID: <20150221183455.GC8406@gmail.com> References: <20150221093150.GA27841@gmail.com> <20150221163840.GA32073@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150221163840.GA32073@pd.tnic> 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 Content-Length: 1062 Lines: 35 * Borislav Petkov wrote: > plain 3.19: > > 234.681331200 seconds time elapsed ( +- 0.15% ) > > eagerfpu=ENABLE > > 234.066525648 seconds time elapsed ( +- 0.19% ) hm, a win of more than 600 milliseconds - more than I'd have expected. I really want to believe this, but I worry about the systematic boot-to-boot noise though, which cannot be eliminated via --repeat 10. Would it be possible to add a simple runtime debug switch to switch between the two FPU modes dynamically via a sysctl? It should not crash tasks I think if it's flipped around on a reasonably idle system, so should allow much better apples-to-apples comparisons with the same kind of page cache layout, etc. Thanks, Ingo -- 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/