From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760189Ab2CVXcb (ORCPT ); Thu, 22 Mar 2012 19:32:31 -0400 Received: from mga14.intel.com ([143.182.124.37]:38224 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752128Ab2CVXca (ORCPT ); Thu, 22 Mar 2012 19:32:30 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="122207242" Subject: [patch] x86, tlb: switch cr3 in leave_mm() only when needed From: Suresh Siddha Reply-To: Suresh Siddha To: Ingo Molnar , "H. Peter Anvin" , Linus Torvalds , Len Brown Cc: LKML Date: Thu, 22 Mar 2012 16:33:39 -0700 Organization: Intel Corp Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.0.3 (3.0.3-1.fc15) Content-Transfer-Encoding: 7bit Message-ID: <1332459220.16101.144.camel@sbsiddha-desk.sc.intel.com> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Suresh Siddha Subject: x86, tlb: switch cr3 in leave_mm() only when needed Currently leave_mm() unconditionally switches the cr3 to swapper_pg_dir. But there is no need to change the cr3, if we already left that mm. intel_idle() for example calls leave_mm() on every deep c-state entry where the CPU flushes the TLB for us. Similarly flush_tlb_all() was also calling leave_mm() whenever the TLB is in LAZY state. Both these paths will be improved with this change. Signed-off-by: Suresh Siddha --- arch/x86/mm/tlb.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index d6c0418..ad695cc 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -61,11 +61,11 @@ static DEFINE_PER_CPU_READ_MOSTLY(int, tlb_vector_offset); */ void leave_mm(int cpu) { + struct mm_struct *active_mm = percpu_read(cpu_tlbstate.active_mm); if (percpu_read(cpu_tlbstate.state) == TLBSTATE_OK) BUG(); - cpumask_clear_cpu(cpu, - mm_cpumask(percpu_read(cpu_tlbstate.active_mm))); - load_cr3(swapper_pg_dir); + if (cpumask_test_and_clear_cpu(cpu, mm_cpumask(active_mm))) + load_cr3(swapper_pg_dir); } EXPORT_SYMBOL_GPL(leave_mm);