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x86/mm/tlb: Do not make is_lazy dirty for no reason

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Blindly writing to is_lazy for no reason, when the written value is
identical to the old value, makes the cacheline dirty for no reason.
Avoid making such writes to prevent cache coherency traffic for no
reason.

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20210220231712.2475218-7-namit@vmware.com
This commit is contained in:
Nadav Amit 2021-02-20 15:17:09 -08:00 committed by Ingo Molnar
parent 2f4305b19f
commit 09c5272e48
1 changed files with 2 additions and 1 deletions
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3
arch/x86/mm/tlb.c
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@ -469,7 +469,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
__flush_tlb_all();
}
#endif
this_cpu_write(cpu_tlbstate_shared.is_lazy, false);
if (was_lazy)
this_cpu_write(cpu_tlbstate_shared.is_lazy, false);
/*
* The membarrier system call requires a full memory barrier and