[PATCH] riscv: mm: try VMA lock-based page fault handling first

[PATCH] riscv: mm: try VMA lock-based page fault handling first

[Jisheng Zhang]

Attempt VMA lock-based page fault handling first, and fall back to the
existing mmap_lock-based handling if that fails.

A simple running the ebizzy benchmark on Lichee Pi 4A shows that
PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
theory, the more CPUs, the bigger improvement, but I don't have any
HW platform which has more than 4 CPUs.

This is the riscv variant of "x86/mm: try VMA lock-based page fault
handling first".

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---
Any performance numbers are welcome! Especially the numbers on HW
platforms with 8 or more CPUs.

 arch/riscv/Kconfig    |  1 +
 arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 62e84fee2cfd..b958f67f9a12 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -42,6 +42,7 @@ config RISCV
 	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
 	select ARCH_SUPPORTS_HUGETLBFS if MMU
 	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
+	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
 	select ARCH_USE_MEMTEST
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 8685f85a7474..eccdddf26f4b 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
 		flags |= FAULT_FLAG_WRITE;
 	else if (cause == EXC_INST_PAGE_FAULT)
 		flags |= FAULT_FLAG_INSTRUCTION;
+#ifdef CONFIG_PER_VMA_LOCK
+	if (!(flags & FAULT_FLAG_USER))
+		goto lock_mmap;
+
+	vma = lock_vma_under_rcu(mm, addr);
+	if (!vma)
+		goto lock_mmap;
+
+	if (unlikely(access_error(cause, vma))) {
+		vma_end_read(vma);
+		goto lock_mmap;
+	}
+
+	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
+	vma_end_read(vma);
+
+	if (!(fault & VM_FAULT_RETRY)) {
+		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+		goto done;
+	}
+	count_vm_vma_lock_event(VMA_LOCK_RETRY);
+
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			no_context(regs, addr);
+		return;
+	}
+lock_mmap:
+#endif /* CONFIG_PER_VMA_LOCK */
+
 retry:
 	mmap_read_lock(mm);
 	vma = find_vma(mm, addr);
@@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
 
 	mmap_read_unlock(mm);
 
+#ifdef CONFIG_PER_VMA_LOCK
+done:
+#endif
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		tsk->thread.bad_cause = cause;
 		mm_fault_error(regs, addr, fault);
-- 
2.40.1

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[Jisheng Zhang]

On Wed, May 24, 2023 at 12:59:42AM +0800, Jisheng Zhang wrote:
> Attempt VMA lock-based page fault handling first, and fall back to the
> existing mmap_lock-based handling if that fails.
> 
> A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> theory, the more CPUs, the bigger improvement, but I don't have any
> HW platform which has more than 4 CPUs.
> 
> This is the riscv variant of "x86/mm: try VMA lock-based page fault
> handling first".
> 
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> Any performance numbers are welcome! Especially the numbers on HW
> platforms with 8 or more CPUs.

PS: run ebizzy as below:
./ebizzy -mTt your_nr_cpus

> 
>  arch/riscv/Kconfig    |  1 +
>  arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 62e84fee2cfd..b958f67f9a12 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -42,6 +42,7 @@ config RISCV
>  	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
>  	select ARCH_SUPPORTS_HUGETLBFS if MMU
>  	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> +	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
>  	select ARCH_USE_MEMTEST
>  	select ARCH_USE_QUEUED_RWLOCKS
>  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index 8685f85a7474..eccdddf26f4b 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
>  		flags |= FAULT_FLAG_WRITE;
>  	else if (cause == EXC_INST_PAGE_FAULT)
>  		flags |= FAULT_FLAG_INSTRUCTION;
> +#ifdef CONFIG_PER_VMA_LOCK
> +	if (!(flags & FAULT_FLAG_USER))
> +		goto lock_mmap;
> +
> +	vma = lock_vma_under_rcu(mm, addr);
> +	if (!vma)
> +		goto lock_mmap;
> +
> +	if (unlikely(access_error(cause, vma))) {
> +		vma_end_read(vma);
> +		goto lock_mmap;
> +	}
> +
> +	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> +	vma_end_read(vma);
> +
> +	if (!(fault & VM_FAULT_RETRY)) {
> +		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> +		goto done;
> +	}
> +	count_vm_vma_lock_event(VMA_LOCK_RETRY);
> +
> +	if (fault_signal_pending(fault, regs)) {
> +		if (!user_mode(regs))
> +			no_context(regs, addr);
> +		return;
> +	}
> +lock_mmap:
> +#endif /* CONFIG_PER_VMA_LOCK */
> +
>  retry:
>  	mmap_read_lock(mm);
>  	vma = find_vma(mm, addr);
> @@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
>  
>  	mmap_read_unlock(mm);
>  
> +#ifdef CONFIG_PER_VMA_LOCK
> +done:
> +#endif
>  	if (unlikely(fault & VM_FAULT_ERROR)) {
>  		tsk->thread.bad_cause = cause;
>  		mm_fault_error(regs, addr, fault);
> -- 
> 2.40.1
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[Jisheng Zhang]

On Wed, May 24, 2023 at 01:11:55AM +0800, Jisheng Zhang wrote:
> On Wed, May 24, 2023 at 12:59:42AM +0800, Jisheng Zhang wrote:
> > Attempt VMA lock-based page fault handling first, and fall back to the
> > existing mmap_lock-based handling if that fails.
> > 
> > A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> > PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> > theory, the more CPUs, the bigger improvement, but I don't have any
> > HW platform which has more than 4 CPUs.
> > 
> > This is the riscv variant of "x86/mm: try VMA lock-based page fault
> > handling first".
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> > Any performance numbers are welcome! Especially the numbers on HW
> > platforms with 8 or more CPUs.
> 
> PS: run ebizzy as below:
> ./ebizzy -mTt your_nr_cpus

Sorry, should be ./ebizzy -mTt 2*your_nr_cpus

> > 
> >  arch/riscv/Kconfig    |  1 +
> >  arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
> >  2 files changed, 34 insertions(+)
> > 
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 62e84fee2cfd..b958f67f9a12 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -42,6 +42,7 @@ config RISCV
> >  	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
> >  	select ARCH_SUPPORTS_HUGETLBFS if MMU
> >  	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> > +	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
> >  	select ARCH_USE_MEMTEST
> >  	select ARCH_USE_QUEUED_RWLOCKS
> >  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> > index 8685f85a7474..eccdddf26f4b 100644
> > --- a/arch/riscv/mm/fault.c
> > +++ b/arch/riscv/mm/fault.c
> > @@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
> >  		flags |= FAULT_FLAG_WRITE;
> >  	else if (cause == EXC_INST_PAGE_FAULT)
> >  		flags |= FAULT_FLAG_INSTRUCTION;
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +	if (!(flags & FAULT_FLAG_USER))
> > +		goto lock_mmap;
> > +
> > +	vma = lock_vma_under_rcu(mm, addr);
> > +	if (!vma)
> > +		goto lock_mmap;
> > +
> > +	if (unlikely(access_error(cause, vma))) {
> > +		vma_end_read(vma);
> > +		goto lock_mmap;
> > +	}
> > +
> > +	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> > +	vma_end_read(vma);
> > +
> > +	if (!(fault & VM_FAULT_RETRY)) {
> > +		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> > +		goto done;
> > +	}
> > +	count_vm_vma_lock_event(VMA_LOCK_RETRY);
> > +
> > +	if (fault_signal_pending(fault, regs)) {
> > +		if (!user_mode(regs))
> > +			no_context(regs, addr);
> > +		return;
> > +	}
> > +lock_mmap:
> > +#endif /* CONFIG_PER_VMA_LOCK */
> > +
> >  retry:
> >  	mmap_read_lock(mm);
> >  	vma = find_vma(mm, addr);
> > @@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
> >  
> >  	mmap_read_unlock(mm);
> >  
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +done:
> > +#endif
> >  	if (unlikely(fault & VM_FAULT_ERROR)) {
> >  		tsk->thread.bad_cause = cause;
> >  		mm_fault_error(regs, addr, fault);
> > -- 
> > 2.40.1
> > 
> > 
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[guoren]

> Attempt VMA lock-based page fault handling first, and fall back to the
> existing mmap_lock-based handling if that fails.
> 
> A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
Good improvement, I think VMA lock is worth to support in riscv.

Please give more details about ebizzy, Is it 
https://github.com/linux-test-project/ltp/blob/master/utils/benchmark/ebizzy-0.3/ebizzy.c
?

> theory, the more CPUs, the bigger improvement, but I don't have any
> HW platform which has more than 4 CPUs.
> 
> This is the riscv variant of "x86/mm: try VMA lock-based page fault
> handling first".
>

How about add Link tag here:
Link: https://lwn.net/Articles/906852/

> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> Any performance numbers are welcome! Especially the numbers on HW
> platforms with 8 or more CPUs.
> 
>  arch/riscv/Kconfig    |  1 +
>  arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 62e84fee2cfd..b958f67f9a12 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -42,6 +42,7 @@ config RISCV
>  	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
>  	select ARCH_SUPPORTS_HUGETLBFS if MMU
>  	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> +	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
>  	select ARCH_USE_MEMTEST
>  	select ARCH_USE_QUEUED_RWLOCKS
>  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index 8685f85a7474..eccdddf26f4b 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
>  		flags |= FAULT_FLAG_WRITE;
>  	else if (cause == EXC_INST_PAGE_FAULT)
>  		flags |= FAULT_FLAG_INSTRUCTION;
> +#ifdef CONFIG_PER_VMA_LOCK
> +	if (!(flags & FAULT_FLAG_USER))
> +		goto lock_mmap;
> +
> +	vma = lock_vma_under_rcu(mm, addr);
> +	if (!vma)
> +		goto lock_mmap;
> +
> +	if (unlikely(access_error(cause, vma))) {
> +		vma_end_read(vma);
> +		goto lock_mmap;
> +	}
> +
> +	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> +	vma_end_read(vma);
> +
> +	if (!(fault & VM_FAULT_RETRY)) {
> +		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> +		goto done;
> +	}
> +	count_vm_vma_lock_event(VMA_LOCK_RETRY);
> +
> +	if (fault_signal_pending(fault, regs)) {
> +		if (!user_mode(regs))
> +			no_context(regs, addr);
> +		return;
> +	}
> +lock_mmap:
> +#endif /* CONFIG_PER_VMA_LOCK */
> +
>  retry:
>  	mmap_read_lock(mm);
>  	vma = find_vma(mm, addr);
> @@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
>  
>  	mmap_read_unlock(mm);
>  
> +#ifdef CONFIG_PER_VMA_LOCK
> +done:
> +#endif
It's very close to cd7f176aea5f ("arm64/mm: try VMA lock-based page fault 
handling first"), and I didn't find any problem. So:

Reviewed-by: Guo Ren <guoren@kernel.org>

F.Y.I Huacai Chen, maybe he also would be interesting this new feature.


>  	if (unlikely(fault & VM_FAULT_ERROR)) {
>  		tsk->thread.bad_cause = cause;
>  		mm_fault_error(regs, addr, fault);
> -- 
> 2.40.1

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[Suren Baghdasaryan]

On Tue, May 23, 2023 at 10:03 PM <guoren@kernel.org> wrote:
>
> > Attempt VMA lock-based page fault handling first, and fall back to the
> > existing mmap_lock-based handling if that fails.
> >
> > A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> > PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> Good improvement, I think VMA lock is worth to support in riscv.
>
> Please give more details about ebizzy, Is it
> https://github.com/linux-test-project/ltp/blob/master/utils/benchmark/ebizzy-0.3/ebizzy.c
> ?
>
> > theory, the more CPUs, the bigger improvement, but I don't have any
> > HW platform which has more than 4 CPUs.
> >
> > This is the riscv variant of "x86/mm: try VMA lock-based page fault
> > handling first".
> >
>
> How about add Link tag here:
> Link: https://lwn.net/Articles/906852/
>
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> > Any performance numbers are welcome! Especially the numbers on HW
> > platforms with 8 or more CPUs.
> >
> >  arch/riscv/Kconfig    |  1 +
> >  arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
> >  2 files changed, 34 insertions(+)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 62e84fee2cfd..b958f67f9a12 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -42,6 +42,7 @@ config RISCV
> >       select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
> >       select ARCH_SUPPORTS_HUGETLBFS if MMU
> >       select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> > +     select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
> >       select ARCH_USE_MEMTEST
> >       select ARCH_USE_QUEUED_RWLOCKS
> >       select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> > index 8685f85a7474..eccdddf26f4b 100644
> > --- a/arch/riscv/mm/fault.c
> > +++ b/arch/riscv/mm/fault.c
> > @@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
> >               flags |= FAULT_FLAG_WRITE;
> >       else if (cause == EXC_INST_PAGE_FAULT)
> >               flags |= FAULT_FLAG_INSTRUCTION;
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +     if (!(flags & FAULT_FLAG_USER))
> > +             goto lock_mmap;
> > +
> > +     vma = lock_vma_under_rcu(mm, addr);
> > +     if (!vma)
> > +             goto lock_mmap;
> > +
> > +     if (unlikely(access_error(cause, vma))) {
> > +             vma_end_read(vma);
> > +             goto lock_mmap;
> > +     }
> > +
> > +     fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> > +     vma_end_read(vma);
> > +
> > +     if (!(fault & VM_FAULT_RETRY)) {
> > +             count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> > +             goto done;
> > +     }
> > +     count_vm_vma_lock_event(VMA_LOCK_RETRY);
> > +
> > +     if (fault_signal_pending(fault, regs)) {
> > +             if (!user_mode(regs))
> > +                     no_context(regs, addr);
> > +             return;
> > +     }
> > +lock_mmap:
> > +#endif /* CONFIG_PER_VMA_LOCK */
> > +
> >  retry:
> >       mmap_read_lock(mm);
> >       vma = find_vma(mm, addr);
> > @@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
> >
> >       mmap_read_unlock(mm);
> >
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +done:
> > +#endif
> It's very close to cd7f176aea5f ("arm64/mm: try VMA lock-based page fault
> handling first"), and I didn't find any problem. So:
>
> Reviewed-by: Guo Ren <guoren@kernel.org>

Looks correct to me.

Reviewed-by: Suren Baghdasaryan <surenb@google.com>

>
> F.Y.I Huacai Chen, maybe he also would be interesting this new feature.
>
>
> >       if (unlikely(fault & VM_FAULT_ERROR)) {
> >               tsk->thread.bad_cause = cause;
> >               mm_fault_error(regs, addr, fault);
> > --
> > 2.40.1

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[Jisheng Zhang]

On Wed, May 24, 2023 at 01:02:59AM -0400, guoren@kernel.org wrote:
> > Attempt VMA lock-based page fault handling first, and fall back to the
> > existing mmap_lock-based handling if that fails.
> > 
> > A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> > PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> Good improvement, I think VMA lock is worth to support in riscv.
> 
> Please give more details about ebizzy, Is it 
> https://github.com/linux-test-project/ltp/blob/master/utils/benchmark/ebizzy-0.3/ebizzy.c
> ?

yeah it's one of ltp benchmark utils.

> 
> > theory, the more CPUs, the bigger improvement, but I don't have any
> > HW platform which has more than 4 CPUs.
> > 
> > This is the riscv variant of "x86/mm: try VMA lock-based page fault
> > handling first".
> >
> 
> How about add Link tag here:
> Link: https://lwn.net/Articles/906852/
> 
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> > Any performance numbers are welcome! Especially the numbers on HW
> > platforms with 8 or more CPUs.
> > 
> >  arch/riscv/Kconfig    |  1 +
> >  arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
> >  2 files changed, 34 insertions(+)
> > 
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 62e84fee2cfd..b958f67f9a12 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -42,6 +42,7 @@ config RISCV
> >  	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
> >  	select ARCH_SUPPORTS_HUGETLBFS if MMU
> >  	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> > +	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU
> >  	select ARCH_USE_MEMTEST
> >  	select ARCH_USE_QUEUED_RWLOCKS
> >  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> > index 8685f85a7474..eccdddf26f4b 100644
> > --- a/arch/riscv/mm/fault.c
> > +++ b/arch/riscv/mm/fault.c
> > @@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
> >  		flags |= FAULT_FLAG_WRITE;
> >  	else if (cause == EXC_INST_PAGE_FAULT)
> >  		flags |= FAULT_FLAG_INSTRUCTION;
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +	if (!(flags & FAULT_FLAG_USER))
> > +		goto lock_mmap;
> > +
> > +	vma = lock_vma_under_rcu(mm, addr);
> > +	if (!vma)
> > +		goto lock_mmap;
> > +
> > +	if (unlikely(access_error(cause, vma))) {
> > +		vma_end_read(vma);
> > +		goto lock_mmap;
> > +	}
> > +
> > +	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> > +	vma_end_read(vma);
> > +
> > +	if (!(fault & VM_FAULT_RETRY)) {
> > +		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> > +		goto done;
> > +	}
> > +	count_vm_vma_lock_event(VMA_LOCK_RETRY);
> > +
> > +	if (fault_signal_pending(fault, regs)) {
> > +		if (!user_mode(regs))
> > +			no_context(regs, addr);
> > +		return;
> > +	}
> > +lock_mmap:
> > +#endif /* CONFIG_PER_VMA_LOCK */
> > +
> >  retry:
> >  	mmap_read_lock(mm);
> >  	vma = find_vma(mm, addr);
> > @@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
> >  
> >  	mmap_read_unlock(mm);
> >  
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +done:
> > +#endif
> It's very close to cd7f176aea5f ("arm64/mm: try VMA lock-based page fault 
> handling first"), and I didn't find any problem. So:
> 
> Reviewed-by: Guo Ren <guoren@kernel.org>
> 
> F.Y.I Huacai Chen, maybe he also would be interesting this new feature.
> 
> 
> >  	if (unlikely(fault & VM_FAULT_ERROR)) {
> >  		tsk->thread.bad_cause = cause;
> >  		mm_fault_error(regs, addr, fault);
> > -- 
> > 2.40.1

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[Palmer Dabbelt]

On Wed, 24 May 2023 00:59:42 +0800, Jisheng Zhang wrote:
> Attempt VMA lock-based page fault handling first, and fall back to the
> existing mmap_lock-based handling if that fails.
> 
> A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> theory, the more CPUs, the bigger improvement, but I don't have any
> HW platform which has more than 4 CPUs.
> 
> [...]

Applied, thanks!

[1/1] riscv: mm: try VMA lock-based page fault handling first
      https://git.kernel.org/palmer/c/648321fa0d97

Best regards,
-- 
Palmer Dabbelt <palmer@rivosinc.com>

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Wed, 24 May 2023 00:59:42 +0800 you wrote:
> Attempt VMA lock-based page fault handling first, and fall back to the
> existing mmap_lock-based handling if that fails.
> 
> A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> theory, the more CPUs, the bigger improvement, but I don't have any
> HW platform which has more than 4 CPUs.
> 
> [...]

Here is the summary with links:
  - riscv: mm: try VMA lock-based page fault handling first
    https://git.kernel.org/riscv/c/648321fa0d97

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH] riscv: mm: try VMA lock-based page fault handling first

[Kefeng Wang]

On 2023/5/24 0:59, Jisheng Zhang wrote:
> Attempt VMA lock-based page fault handling first, and fall back to the
> existing mmap_lock-based handling if that fails.
> 
> A simple running the ebizzy benchmark on Lichee Pi 4A shows that
> PER_VMA_LOCK can improve the ebizzy benchmark by about 32.68%. In
> theory, the more CPUs, the bigger improvement, but I don't have any
> HW platform which has more than 4 CPUs.
> 
> This is the riscv variant of "x86/mm: try VMA lock-based page fault
> handling first".
> 
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> Any performance numbers are welcome! Especially the numbers on HW
> platforms with 8 or more CPUs.
> 
>   arch/riscv/Kconfig    |  1 +
>   arch/riscv/mm/fault.c | 33 +++++++++++++++++++++++++++++++++
>   2 files changed, 34 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 62e84fee2cfd..b958f67f9a12 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -42,6 +42,7 @@ config RISCV
>   	select ARCH_SUPPORTS_DEBUG_PAGEALLOC if MMU
>   	select ARCH_SUPPORTS_HUGETLBFS if MMU
>   	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
> +	select ARCH_SUPPORTS_PER_VMA_LOCK if MMU

no need if mmu，  see PER_VMA_LOCK


config PER_VMA_LOCK
         bool "allow VMA lock-based page fault"
         def_bool y
         depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP

Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>

>   	select ARCH_USE_MEMTEST
>   	select ARCH_USE_QUEUED_RWLOCKS
>   	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index 8685f85a7474..eccdddf26f4b 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -286,6 +286,36 @@ void handle_page_fault(struct pt_regs *regs)
>   		flags |= FAULT_FLAG_WRITE;
>   	else if (cause == EXC_INST_PAGE_FAULT)
>   		flags |= FAULT_FLAG_INSTRUCTION;
> +#ifdef CONFIG_PER_VMA_LOCK
> +	if (!(flags & FAULT_FLAG_USER))
> +		goto lock_mmap;
> +
> +	vma = lock_vma_under_rcu(mm, addr);
> +	if (!vma)
> +		goto lock_mmap;
> +
> +	if (unlikely(access_error(cause, vma))) {
> +		vma_end_read(vma);
> +		goto lock_mmap;
> +	}
> +
> +	fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> +	vma_end_read(vma);
> +
> +	if (!(fault & VM_FAULT_RETRY)) {
> +		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> +		goto done;
> +	}
> +	count_vm_vma_lock_event(VMA_LOCK_RETRY);
> +
> +	if (fault_signal_pending(fault, regs)) {
> +		if (!user_mode(regs))
> +			no_context(regs, addr);
> +		return;
> +	}
> +lock_mmap:
> +#endif /* CONFIG_PER_VMA_LOCK */
> +
>   retry:
>   	mmap_read_lock(mm);
>   	vma = find_vma(mm, addr);
> @@ -355,6 +385,9 @@ void handle_page_fault(struct pt_regs *regs)
>   
>   	mmap_read_unlock(mm);
>   
> +#ifdef CONFIG_PER_VMA_LOCK
> +done:
> +#endif
>   	if (unlikely(fault & VM_FAULT_ERROR)) {
>   		tsk->thread.bad_cause = cause;
>   		mm_fault_error(regs, addr, fault);