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Message-ID: <1332459220.16101.144.camel@sbsiddha-desk.sc.intel.com>
Date: Thu, 22 Mar 2012 16:33:39 -0700
From: Suresh Siddha <suresh.b.siddha@...el.com>
To: Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Len Brown <lenb@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: [patch] x86, tlb: switch cr3 in leave_mm() only when needed
From: Suresh Siddha <suresh.b.siddha@...el.com>
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 <suresh.b.siddha@...el.com>
---
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);
--
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