Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755386AbbBTS6Y (ORCPT ); Fri, 20 Feb 2015 13:58:24 -0500 Received: from mail-pa0-f45.google.com ([209.85.220.45]:40488 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755361AbbBTS6V (ORCPT ); Fri, 20 Feb 2015 13:58:21 -0500 From: Andy Lutomirski To: Oleg Nesterov , Rik van Riel , x86@kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov Cc: Andy Lutomirski Subject: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs Date: Fri, 20 Feb 2015 10:58:15 -0800 Message-Id: X-Mailer: git-send-email 2.1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1674 Lines: 45 We have eager and lazy fpu modes, introduced in: 304bceda6a18 x86, fpu: use non-lazy fpu restore for processors supporting xsave The result is rather messy. There are two code paths in almost all of the FPU code, and only one of them (the eager case) is tested frequently, since most kernel developers have new enough hardware that we use eagerfpu. It seems that, on any remotely recent hardware, eagerfpu is a win: glibc uses SSE2, so laziness is probably overoptimistic, and, in any case, manipulating TS is far slower that saving and restoring the full state. To try to shake out any latent issues on old hardware, this changes the default to eager on all CPUs. If no performance or functionality problems show up, a subsequent patch could remove lazy mode entirely. Signed-off-by: Andy Lutomirski --- arch/x86/kernel/xsave.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index 0de1fae2bdf0..1928c8f34ce5 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -637,8 +637,8 @@ static void __init xstate_enable_boot_cpu(void) prepare_fx_sw_frame(); setup_init_fpu_buf(); - /* Auto enable eagerfpu for xsaveopt */ - if (cpu_has_xsaveopt && eagerfpu != DISABLE) + /* Auto enable eagerfpu for everyone */ + if (eagerfpu != DISABLE) eagerfpu = ENABLE; if (pcntxt_mask & XSTATE_EAGER) { -- 2.1.0 -- 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/