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* [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally
@ 2019-09-23 21:30 Leonardo Bras
  2019-09-24  1:22 ` Leonardo Bras
  0 siblings, 1 reply; 6+ messages in thread
From: Leonardo Bras @ 2019-09-23 21:30 UTC (permalink / raw)
  To: linuxppc-dev, linux-kernel, kvm, kvm-ppc
  Cc: Leonardo Bras, Paul Mackerras, Benjamin Herrenschmidt, Michael Ellerman

Reduces the number of calls to get_current() in order to get the value of
current->mm by doing it once and storing the value, since it is not
supposed to change inside the same process).

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
---
Re-sending to all lists involved. (I missed kvm ones)

 arch/powerpc/kvm/book3s_64_mmu_hv.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 9a75f0e1933b..f2b9aea43216 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -508,6 +508,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	struct vm_area_struct *vma;
 	unsigned long rcbits;
 	long mmio_update;
+	struct mm_struct *mm;
 
 	if (kvm_is_radix(kvm))
 		return kvmppc_book3s_radix_page_fault(run, vcpu, ea, dsisr);
@@ -584,6 +585,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	is_ci = false;
 	pfn = 0;
 	page = NULL;
+	mm = current->mm;
 	pte_size = PAGE_SIZE;
 	writing = (dsisr & DSISR_ISSTORE) != 0;
 	/* If writing != 0, then the HPTE must allow writing, if we get here */
@@ -592,8 +594,8 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	npages = get_user_pages_fast(hva, 1, writing ? FOLL_WRITE : 0, pages);
 	if (npages < 1) {
 		/* Check if it's an I/O mapping */
-		down_read(&current->mm->mmap_sem);
-		vma = find_vma(current->mm, hva);
+		down_read(&mm->mmap_sem);
+		vma = find_vma(mm, hva);
 		if (vma && vma->vm_start <= hva && hva + psize <= vma->vm_end &&
 		    (vma->vm_flags & VM_PFNMAP)) {
 			pfn = vma->vm_pgoff +
@@ -602,7 +604,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			is_ci = pte_ci(__pte((pgprot_val(vma->vm_page_prot))));
 			write_ok = vma->vm_flags & VM_WRITE;
 		}
-		up_read(&current->mm->mmap_sem);
+		up_read(&mm->mmap_sem);
 		if (!pfn)
 			goto out_put;
 	} else {
@@ -621,8 +623,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			 * hugepage split and collapse.
 			 */
 			local_irq_save(flags);
-			ptep = find_current_mm_pte(current->mm->pgd,
-						   hva, NULL, NULL);
+			ptep = find_current_mm_pte(mm->pgd, hva, NULL, NULL);
 			if (ptep) {
 				pte = kvmppc_read_update_linux_pte(ptep, 1);
 				if (__pte_write(pte))
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* Re: [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally
  2019-09-23 21:30 [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally Leonardo Bras
@ 2019-09-24  1:22 ` Leonardo Bras
  0 siblings, 0 replies; 6+ messages in thread
From: Leonardo Bras @ 2019-09-24  1:22 UTC (permalink / raw)
  To: linuxppc-dev, linux-kernel, kvm, kvm-ppc
  Cc: Paul Mackerras, Benjamin Herrenschmidt, Michael Ellerman

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I have done a very simple comparison with gdb disassemble:
By applying this patch, there was a reduction in the function size from
882 to 878 instructions.

(It's a resend, due to not having all the correct lists on my previous
mail) 

On Mon, 2019-09-23 at 18:30 -0300, Leonardo Bras wrote:
> Reduces the number of calls to get_current() in order to get the value of
> current->mm by doing it once and storing the value, since it is not
> supposed to change inside the same process).
> 
> Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
> ---
> Re-sending to all lists involved. (I missed kvm ones)
> 
>  arch/powerpc/kvm/book3s_64_mmu_hv.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 9a75f0e1933b..f2b9aea43216 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -508,6 +508,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	struct vm_area_struct *vma;
>  	unsigned long rcbits;
>  	long mmio_update;
> +	struct mm_struct *mm;
>  
>  	if (kvm_is_radix(kvm))
>  		return kvmppc_book3s_radix_page_fault(run, vcpu, ea, dsisr);
> @@ -584,6 +585,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	is_ci = false;
>  	pfn = 0;
>  	page = NULL;
> +	mm = current->mm;
>  	pte_size = PAGE_SIZE;
>  	writing = (dsisr & DSISR_ISSTORE) != 0;
>  	/* If writing != 0, then the HPTE must allow writing, if we get here */
> @@ -592,8 +594,8 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	npages = get_user_pages_fast(hva, 1, writing ? FOLL_WRITE : 0, pages);
>  	if (npages < 1) {
>  		/* Check if it's an I/O mapping */
> -		down_read(&current->mm->mmap_sem);
> -		vma = find_vma(current->mm, hva);
> +		down_read(&mm->mmap_sem);
> +		vma = find_vma(mm, hva);
>  		if (vma && vma->vm_start <= hva && hva + psize <= vma->vm_end &&
>  		    (vma->vm_flags & VM_PFNMAP)) {
>  			pfn = vma->vm_pgoff +
> @@ -602,7 +604,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			is_ci = pte_ci(__pte((pgprot_val(vma->vm_page_prot))));
>  			write_ok = vma->vm_flags & VM_WRITE;
>  		}
> -		up_read(&current->mm->mmap_sem);
> +		up_read(&mm->mmap_sem);
>  		if (!pfn)
>  			goto out_put;
>  	} else {
> @@ -621,8 +623,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			 * hugepage split and collapse.
>  			 */
>  			local_irq_save(flags);
> -			ptep = find_current_mm_pte(current->mm->pgd,
> -						   hva, NULL, NULL);
> +			ptep = find_current_mm_pte(mm->pgd, hva, NULL, NULL);
>  			if (ptep) {
>  				pte = kvmppc_read_update_linux_pte(ptep, 1);
>  				if (__pte_write(pte))

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^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally
  2019-09-23 18:35   ` Leonardo Bras
@ 2019-09-23 19:12     ` Leonardo Bras
  0 siblings, 0 replies; 6+ messages in thread
From: Leonardo Bras @ 2019-09-23 19:12 UTC (permalink / raw)
  To: PaulMackerras, linuxppc-dev, linux-kernel

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On Mon, 2019-09-23 at 15:35 -0300, Leonardo Bras wrote:
> Could you please provide feedback on this patch?

I have done a very simple comparison with gcc disassemble:
By applying this patch, there was a reduction in the function size from
882 to 878 instructions.

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^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally
  2019-09-20  2:47 ` Leonardo Bras
@ 2019-09-23 18:35   ` Leonardo Bras
  2019-09-23 19:12     ` Leonardo Bras
  0 siblings, 1 reply; 6+ messages in thread
From: Leonardo Bras @ 2019-09-23 18:35 UTC (permalink / raw)
  To: PaulMackerras, linuxppc-dev, linux-kernel

[-- Attachment #1: Type: text/plain, Size: 441 bytes --]

On Thu, 2019-09-19 at 23:47 -0300, Leonardo Bras wrote:
> Hello Paul, 
> I sent this patch, but I have a question:
> 
> > +	mm = current->mm;
> 
> Here, current->mm is not always the same as kvm->mm? 
> Thanks


I have contacted Paul, who said it is equivalent. But I think I will
deal with that on another patch series, as it's another issue.

Could you please provide feedback on this patch?

Best regards, 
Leonardo Bras

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^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally
  2019-09-19 22:27 Leonardo Bras
@ 2019-09-20  2:47 ` Leonardo Bras
  2019-09-23 18:35   ` Leonardo Bras
  0 siblings, 1 reply; 6+ messages in thread
From: Leonardo Bras @ 2019-09-20  2:47 UTC (permalink / raw)
  To: PaulMackerras, linuxppc-dev, linux-kernel

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Hello Paul, 
I sent this patch, but I have a question:

On Thu, 2019-09-19 at 19:27 -0300, Leonardo Bras wrote:
> Reduces the number of calls to get_current() in order to get the value of
> current->mm by doing it once and storing the value, since it is not
> supposed to change inside the same process).
> 
> Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
> ---
>  arch/powerpc/kvm/book3s_64_mmu_hv.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> index 9a75f0e1933b..f2b9aea43216 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
> @@ -508,6 +508,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	struct vm_area_struct *vma;
>  	unsigned long rcbits;
>  	long mmio_update;
> +	struct mm_struct *mm;
>  
>  	if (kvm_is_radix(kvm))
>  		return kvmppc_book3s_radix_page_fault(run, vcpu, ea, dsisr);
> @@ -584,6 +585,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	is_ci = false;
>  	pfn = 0;
>  	page = NULL;
> +	mm = current->mm;

Here, current->mm is not always the same as kvm->mm? 

>  	pte_size = PAGE_SIZE;
>  	writing = (dsisr & DSISR_ISSTORE) != 0;
>  	/* If writing != 0, then the HPTE must allow writing, if we get here */
> @@ -592,8 +594,8 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  	npages = get_user_pages_fast(hva, 1, writing ? FOLL_WRITE : 0, pages);
>  	if (npages < 1) {
>  		/* Check if it's an I/O mapping */
> -		down_read(&current->mm->mmap_sem);
> -		vma = find_vma(current->mm, hva);
> +		down_read(&mm->mmap_sem);
> +		vma = find_vma(mm, hva);
>  		if (vma && vma->vm_start <= hva && hva + psize <= vma->vm_end &&
>  		    (vma->vm_flags & VM_PFNMAP)) {
>  			pfn = vma->vm_pgoff +
> @@ -602,7 +604,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			is_ci = pte_ci(__pte((pgprot_val(vma->vm_page_prot))));
>  			write_ok = vma->vm_flags & VM_WRITE;
>  		}
> -		up_read(&current->mm->mmap_sem);
> +		up_read(&mm->mmap_sem);
>  		if (!pfn)
>  			goto out_put;
>  	} else {
> @@ -621,8 +623,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
>  			 * hugepage split and collapse.
>  			 */
>  			local_irq_save(flags);
> -			ptep = find_current_mm_pte(current->mm->pgd,
> -						   hva, NULL, NULL);
> +			ptep = find_current_mm_pte(mm->pgd, hva, NULL, NULL);
>  			if (ptep) {
>  				pte = kvmppc_read_update_linux_pte(ptep, 1);
>  				if (__pte_write(pte))

Thanks !

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^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally
@ 2019-09-19 22:27 Leonardo Bras
  2019-09-20  2:47 ` Leonardo Bras
  0 siblings, 1 reply; 6+ messages in thread
From: Leonardo Bras @ 2019-09-19 22:27 UTC (permalink / raw)
  To: linuxppc-dev, linux-kernel
  Cc: Leonardo Bras, Paul Mackerras, Benjamin Herrenschmidt, Michael Ellerman

Reduces the number of calls to get_current() in order to get the value of
current->mm by doing it once and storing the value, since it is not
supposed to change inside the same process).

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 9a75f0e1933b..f2b9aea43216 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -508,6 +508,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	struct vm_area_struct *vma;
 	unsigned long rcbits;
 	long mmio_update;
+	struct mm_struct *mm;
 
 	if (kvm_is_radix(kvm))
 		return kvmppc_book3s_radix_page_fault(run, vcpu, ea, dsisr);
@@ -584,6 +585,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	is_ci = false;
 	pfn = 0;
 	page = NULL;
+	mm = current->mm;
 	pte_size = PAGE_SIZE;
 	writing = (dsisr & DSISR_ISSTORE) != 0;
 	/* If writing != 0, then the HPTE must allow writing, if we get here */
@@ -592,8 +594,8 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	npages = get_user_pages_fast(hva, 1, writing ? FOLL_WRITE : 0, pages);
 	if (npages < 1) {
 		/* Check if it's an I/O mapping */
-		down_read(&current->mm->mmap_sem);
-		vma = find_vma(current->mm, hva);
+		down_read(&mm->mmap_sem);
+		vma = find_vma(mm, hva);
 		if (vma && vma->vm_start <= hva && hva + psize <= vma->vm_end &&
 		    (vma->vm_flags & VM_PFNMAP)) {
 			pfn = vma->vm_pgoff +
@@ -602,7 +604,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			is_ci = pte_ci(__pte((pgprot_val(vma->vm_page_prot))));
 			write_ok = vma->vm_flags & VM_WRITE;
 		}
-		up_read(&current->mm->mmap_sem);
+		up_read(&mm->mmap_sem);
 		if (!pfn)
 			goto out_put;
 	} else {
@@ -621,8 +623,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			 * hugepage split and collapse.
 			 */
 			local_irq_save(flags);
-			ptep = find_current_mm_pte(current->mm->pgd,
-						   hva, NULL, NULL);
+			ptep = find_current_mm_pte(mm->pgd, hva, NULL, NULL);
 			if (ptep) {
 				pte = kvmppc_read_update_linux_pte(ptep, 1);
 				if (__pte_write(pte))
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-09-24  1:22 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2019-09-23 21:30 [PATCH 1/1] powerpc: kvm: Reduce calls to get current->mm by storing the value locally Leonardo Bras
2019-09-24  1:22 ` Leonardo Bras
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2019-09-19 22:27 Leonardo Bras
2019-09-20  2:47 ` Leonardo Bras
2019-09-23 18:35   ` Leonardo Bras
2019-09-23 19:12     ` Leonardo Bras

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