From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932814Ab2EJXa7 (ORCPT ); Thu, 10 May 2012 19:30:59 -0400 Received: from mga11.intel.com ([192.55.52.93]:18333 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932879Ab2EJXad (ORCPT ); Thu, 10 May 2012 19:30:33 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="164690668" From: Suresh Siddha To: torvalds@linux-foundation.org, hpa@zytor.com, mingo@elte.hu, oleg@redhat.com Cc: Suresh Siddha , linux-kernel@vger.kernel.org, suresh@aristanetworks.com Subject: [PATCH v2 4/4] x86, fpu: drop the fpu state during thread exit Date: Thu, 10 May 2012 16:33:31 -0700 Message-Id: <1336692811-30576-4-git-send-email-suresh.b.siddha@intel.com> X-Mailer: git-send-email 1.7.6.5 In-Reply-To: <1336692811-30576-1-git-send-email-suresh.b.siddha@intel.com> References: <1336692811-30576-1-git-send-email-suresh.b.siddha@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is no need to save any active fpu state to the task structure memory if the task is dead. Just drop the state instead. For example, this saved some 1770 xsave's during the system boot of a two socket Xeon system. Suggested-by: Linus Torvalds Signed-off-by: Suresh Siddha --- arch/x86/kernel/process.c | 19 +++++++++++++------ 1 files changed, 13 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index b7e1e0e..1219fe2 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -87,6 +87,16 @@ void arch_task_cache_init(void) SLAB_PANIC | SLAB_NOTRACK, NULL); } +static inline void drop_fpu(struct task_struct *tsk) +{ + /* + * Forget coprocessor state.. + */ + tsk->fpu_counter = 0; + clear_fpu(tsk); + clear_used_math(); +} + /* * Free current thread data structures etc.. */ @@ -109,6 +119,8 @@ void exit_thread(void) put_cpu(); kfree(bp); } + + drop_fpu(me); } void show_regs(struct pt_regs *regs) @@ -149,12 +161,7 @@ void flush_thread(void) flush_ptrace_hw_breakpoint(tsk); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); - /* - * Forget coprocessor state.. - */ - tsk->fpu_counter = 0; - clear_fpu(tsk); - clear_used_math(); + drop_fpu(tsk); } static void hard_disable_TSC(void) -- 1.7.6.5