* [PATCH] MIPS: smp: optimization for flush_tlb_mm when exiting
@ 2022-05-10 11:44 Mao Bibo
2022-05-12 16:11 ` Thomas Bogendoerfer
0 siblings, 1 reply; 2+ messages in thread
From: Mao Bibo @ 2022-05-10 11:44 UTC (permalink / raw)
To: Thomas Bogendoerfer; +Cc: linux-mips, linux-kernel
When process exits or execute new binary, it will call function
exit_mmap with old mm, there is such function call trace:
exit_mmap(struct mm_struct *mm)
--> tlb_finish_mmu(&tlb, 0, -1)
--> arch_tlb_finish_mmu(tlb, start, end, force)
--> tlb_flush_mmu(tlb);
--> tlb_flush(struct mmu_gather *tlb)
--> flush_tlb_mm(tlb->mm)
It is not necessary to flush tlb since oldmm is not used anymore
by the process, there is similar operations on IA64/ARM64 etc,
this patch adds such optimization on MIPS.
Signed-off-by: Mao Bibo <maobibo@loongson.cn>
---
arch/mips/kernel/smp.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 1986d1309410..1d93b85271ba 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -518,6 +518,12 @@ static inline void smp_on_each_tlb(void (*func) (void *info), void *info)
void flush_tlb_mm(struct mm_struct *mm)
{
+ if (!mm)
+ return;
+
+ if (atomic_read(&mm->mm_users) == 0)
+ return; /* happens as a result of exit_mmap() */
+
preempt_disable();
if (cpu_has_mmid) {
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] MIPS: smp: optimization for flush_tlb_mm when exiting
2022-05-10 11:44 [PATCH] MIPS: smp: optimization for flush_tlb_mm when exiting Mao Bibo
@ 2022-05-12 16:11 ` Thomas Bogendoerfer
0 siblings, 0 replies; 2+ messages in thread
From: Thomas Bogendoerfer @ 2022-05-12 16:11 UTC (permalink / raw)
To: Mao Bibo; +Cc: linux-mips, linux-kernel
On Tue, May 10, 2022 at 07:44:41PM +0800, Mao Bibo wrote:
> When process exits or execute new binary, it will call function
> exit_mmap with old mm, there is such function call trace:
> exit_mmap(struct mm_struct *mm)
> --> tlb_finish_mmu(&tlb, 0, -1)
> --> arch_tlb_finish_mmu(tlb, start, end, force)
> --> tlb_flush_mmu(tlb);
> --> tlb_flush(struct mmu_gather *tlb)
> --> flush_tlb_mm(tlb->mm)
>
> It is not necessary to flush tlb since oldmm is not used anymore
> by the process, there is similar operations on IA64/ARM64 etc,
> this patch adds such optimization on MIPS.
>
> Signed-off-by: Mao Bibo <maobibo@loongson.cn>
> ---
> arch/mips/kernel/smp.c | 6 ++++++
> 1 file changed, 6 insertions(+)
applied to mips-next.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
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