Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757591Ab2EHXPG (ORCPT ); Tue, 8 May 2012 19:15:06 -0400 Received: from mga02.intel.com ([134.134.136.20]:37903 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757141Ab2EHXPD (ORCPT ); Tue, 8 May 2012 19:15:03 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="138405397" 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 3/3] x86, fpu: clear the fpu state during thread exit Date: Tue, 8 May 2012 16:18:05 -0700 Message-Id: <1336519085-27450-4-git-send-email-suresh.b.siddha@intel.com> X-Mailer: git-send-email 1.7.6.5 In-Reply-To: <1336519085-27450-1-git-send-email-suresh.b.siddha@intel.com> References: <1336421341.19423.4.camel@sbsiddha-desk.sc.intel.com> <1336519085-27450-1-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 Content-Length: 1641 Lines: 64 There is no need to save any active fpu state to the task structure memory if the task is dead. Just clear 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 1d92a5a..1c7566e 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -81,6 +81,16 @@ void arch_task_cache_init(void) SLAB_PANIC | SLAB_NOTRACK, NULL); } +static inline void flush_fpu(struct task_struct *tsk) +{ + /* + * Forget coprocessor state.. + */ + tsk->fpu_counter = 0; + clear_fpu(tsk); + clear_used_math(); +} + /* * Free current thread data structures etc.. */ @@ -103,6 +113,8 @@ void exit_thread(void) put_cpu(); kfree(bp); } + + flush_fpu(me); } void show_regs(struct pt_regs *regs) @@ -143,12 +155,7 @@ 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(); + flush_fpu(tsk); } static void hard_disable_TSC(void) -- 1.7.6.5 -- 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/