* [PATCH] ANDROID: binder: change down_write to down_read
@ 2018-03-28 2:42 Minchan Kim
2018-03-28 5:53 ` Greg Kroah-Hartman
2018-03-28 7:18 ` Martijn Coenen
0 siblings, 2 replies; 4+ messages in thread
From: Minchan Kim @ 2018-03-28 2:42 UTC (permalink / raw)
To: LKML; +Cc: Minchan Kim, Martijn Coenen, Todd Kjos, Greg Kroah-Hartman
binder_update_page_range needs down_write of mmap_sem because
vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless
it is set. However, when I profile binder working, it seems
every binder buffers should be mapped in advance by binder_mmap.
It means we could set VM_MIXEDMAP in bider_mmap time which is
already hold a mmap_sem as down_write so binder_update_page_range
doesn't need to hold a mmap_sem as down_write.
Android suffers from mmap_sem contention so let's reduce mmap_sem
down_write.
Cc: Martijn Coenen <maco@android.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
drivers/android/binder.c | 2 +-
drivers/android/binder_alloc.c | 8 +++++---
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 764b63a5aade..9a14c6dd60c4 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4722,7 +4722,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
failure_string = "bad vm_flags";
goto err_bad_arg;
}
- vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE;
+ vma->vm_flags |= (VM_DONTCOPY | VM_MIXEDMAP) & ~VM_MAYWRITE;
vma->vm_ops = &binder_vm_ops;
vma->vm_private_data = proc;
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 5a426c877dfb..a184bf12eb15 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
mm = alloc->vma_vm_mm;
if (mm) {
- down_write(&mm->mmap_sem);
+ down_read(&mm->mmap_sem);
vma = alloc->vma;
}
@@ -229,6 +229,8 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
goto err_no_vma;
}
+ WARN_ON_ONCE(vma && !(vma->vm_flags & VM_MIXEDMAP));
+
for (page_addr = start; page_addr < end; page_addr += PAGE_SIZE) {
int ret;
bool on_lru;
@@ -288,7 +290,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
/* vm_insert_page does not seem to increment the refcount */
}
if (mm) {
- up_write(&mm->mmap_sem);
+ up_read(&mm->mmap_sem);
mmput(mm);
}
return 0;
@@ -321,7 +323,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
}
err_no_vma:
if (mm) {
- up_write(&mm->mmap_sem);
+ up_read(&mm->mmap_sem);
mmput(mm);
}
return vma ? -ENOMEM : -ESRCH;
--
2.17.0.rc1.321.gba9d0f2565-goog
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] ANDROID: binder: change down_write to down_read
2018-03-28 2:42 [PATCH] ANDROID: binder: change down_write to down_read Minchan Kim
@ 2018-03-28 5:53 ` Greg Kroah-Hartman
2018-03-28 6:47 ` Minchan Kim
2018-03-28 7:18 ` Martijn Coenen
1 sibling, 1 reply; 4+ messages in thread
From: Greg Kroah-Hartman @ 2018-03-28 5:53 UTC (permalink / raw)
To: Minchan Kim; +Cc: LKML, Martijn Coenen, Todd Kjos
On Wed, Mar 28, 2018 at 11:42:31AM +0900, Minchan Kim wrote:
> binder_update_page_range needs down_write of mmap_sem because
> vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless
> it is set. However, when I profile binder working, it seems
> every binder buffers should be mapped in advance by binder_mmap.
> It means we could set VM_MIXEDMAP in bider_mmap time which is
> already hold a mmap_sem as down_write so binder_update_page_range
> doesn't need to hold a mmap_sem as down_write.
>
> Android suffers from mmap_sem contention so let's reduce mmap_sem
> down_write.
>
> Cc: Martijn Coenen <maco@android.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> drivers/android/binder.c | 2 +-
> drivers/android/binder_alloc.c | 8 +++++---
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 764b63a5aade..9a14c6dd60c4 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -4722,7 +4722,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
> failure_string = "bad vm_flags";
> goto err_bad_arg;
> }
> - vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE;
> + vma->vm_flags |= (VM_DONTCOPY | VM_MIXEDMAP) & ~VM_MAYWRITE;
> vma->vm_ops = &binder_vm_ops;
> vma->vm_private_data = proc;
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 5a426c877dfb..a184bf12eb15 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> mm = alloc->vma_vm_mm;
>
> if (mm) {
> - down_write(&mm->mmap_sem);
> + down_read(&mm->mmap_sem);
> vma = alloc->vma;
> }
>
> @@ -229,6 +229,8 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> goto err_no_vma;
> }
>
> + WARN_ON_ONCE(vma && !(vma->vm_flags & VM_MIXEDMAP));
What can we do with this warning? What about systems that run in 'panic
on warn' mode? Is this something we should handle directly instead?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] ANDROID: binder: change down_write to down_read
2018-03-28 5:53 ` Greg Kroah-Hartman
@ 2018-03-28 6:47 ` Minchan Kim
0 siblings, 0 replies; 4+ messages in thread
From: Minchan Kim @ 2018-03-28 6:47 UTC (permalink / raw)
To: Greg Kroah-Hartman; +Cc: LKML, Martijn Coenen, Todd Kjos
On Wed, Mar 28, 2018 at 07:53:54AM +0200, Greg Kroah-Hartman wrote:
> On Wed, Mar 28, 2018 at 11:42:31AM +0900, Minchan Kim wrote:
> > binder_update_page_range needs down_write of mmap_sem because
> > vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless
> > it is set. However, when I profile binder working, it seems
> > every binder buffers should be mapped in advance by binder_mmap.
> > It means we could set VM_MIXEDMAP in bider_mmap time which is
> > already hold a mmap_sem as down_write so binder_update_page_range
> > doesn't need to hold a mmap_sem as down_write.
> >
> > Android suffers from mmap_sem contention so let's reduce mmap_sem
> > down_write.
> >
> > Cc: Martijn Coenen <maco@android.com>
> > Cc: Todd Kjos <tkjos@google.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > ---
> > drivers/android/binder.c | 2 +-
> > drivers/android/binder_alloc.c | 8 +++++---
> > 2 files changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> > index 764b63a5aade..9a14c6dd60c4 100644
> > --- a/drivers/android/binder.c
> > +++ b/drivers/android/binder.c
> > @@ -4722,7 +4722,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
> > failure_string = "bad vm_flags";
> > goto err_bad_arg;
> > }
> > - vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE;
> > + vma->vm_flags |= (VM_DONTCOPY | VM_MIXEDMAP) & ~VM_MAYWRITE;
> > vma->vm_ops = &binder_vm_ops;
> > vma->vm_private_data = proc;
> >
> > diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> > index 5a426c877dfb..a184bf12eb15 100644
> > --- a/drivers/android/binder_alloc.c
> > +++ b/drivers/android/binder_alloc.c
> > @@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> > mm = alloc->vma_vm_mm;
> >
> > if (mm) {
> > - down_write(&mm->mmap_sem);
> > + down_read(&mm->mmap_sem);
> > vma = alloc->vma;
> > }
> >
> > @@ -229,6 +229,8 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> > goto err_no_vma;
> > }
> >
> > + WARN_ON_ONCE(vma && !(vma->vm_flags & VM_MIXEDMAP));
>
> What can we do with this warning? What about systems that run in 'panic
> on warn' mode? Is this something we should handle directly instead?
Hmm, it seems we don't need above warning there because vm_insert_page will hit
BUG_ON in that case. I will remove it at respin. Thanks for the review, Greg.
I will wait other binder maintainer's opinion about below question.
> > it seems
> > every binder buffers should be mapped in advance by binder_mmap.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] ANDROID: binder: change down_write to down_read
2018-03-28 2:42 [PATCH] ANDROID: binder: change down_write to down_read Minchan Kim
2018-03-28 5:53 ` Greg Kroah-Hartman
@ 2018-03-28 7:18 ` Martijn Coenen
1 sibling, 0 replies; 4+ messages in thread
From: Martijn Coenen @ 2018-03-28 7:18 UTC (permalink / raw)
To: Minchan Kim; +Cc: LKML, Todd Kjos, Greg Kroah-Hartman
On Wed, Mar 28, 2018 at 4:42 AM, Minchan Kim <minchan@kernel.org> wrote:
> binder_update_page_range needs down_write of mmap_sem because
> vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless
> it is set. However, when I profile binder working, it seems
> every binder buffers should be mapped in advance by binder_mmap.
Yeah this is correct - before doing any binder transactions
binder_mmap() must be called, and we do fail transactions if that
hasn't been done yet. LGTM once you're removed the WARN_ON.
Martijn
> It means we could set VM_MIXEDMAP in bider_mmap time which is
> already hold a mmap_sem as down_write so binder_update_page_range
> doesn't need to hold a mmap_sem as down_write.
>
> Android suffers from mmap_sem contention so let's reduce mmap_sem
> down_write.
>
> Cc: Martijn Coenen <maco@android.com>
> Cc: Todd Kjos <tkjos@google.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> drivers/android/binder.c | 2 +-
> drivers/android/binder_alloc.c | 8 +++++---
> 2 files changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 764b63a5aade..9a14c6dd60c4 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -4722,7 +4722,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
> failure_string = "bad vm_flags";
> goto err_bad_arg;
> }
> - vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE;
> + vma->vm_flags |= (VM_DONTCOPY | VM_MIXEDMAP) & ~VM_MAYWRITE;
> vma->vm_ops = &binder_vm_ops;
> vma->vm_private_data = proc;
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 5a426c877dfb..a184bf12eb15 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -219,7 +219,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> mm = alloc->vma_vm_mm;
>
> if (mm) {
> - down_write(&mm->mmap_sem);
> + down_read(&mm->mmap_sem);
> vma = alloc->vma;
> }
>
> @@ -229,6 +229,8 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> goto err_no_vma;
> }
>
> + WARN_ON_ONCE(vma && !(vma->vm_flags & VM_MIXEDMAP));
> +
> for (page_addr = start; page_addr < end; page_addr += PAGE_SIZE) {
> int ret;
> bool on_lru;
> @@ -288,7 +290,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> /* vm_insert_page does not seem to increment the refcount */
> }
> if (mm) {
> - up_write(&mm->mmap_sem);
> + up_read(&mm->mmap_sem);
> mmput(mm);
> }
> return 0;
> @@ -321,7 +323,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
> }
> err_no_vma:
> if (mm) {
> - up_write(&mm->mmap_sem);
> + up_read(&mm->mmap_sem);
> mmput(mm);
> }
> return vma ? -ENOMEM : -ESRCH;
> --
> 2.17.0.rc1.321.gba9d0f2565-goog
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-03-28 7:18 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2018-03-28 2:42 [PATCH] ANDROID: binder: change down_write to down_read Minchan Kim
2018-03-28 5:53 ` Greg Kroah-Hartman
2018-03-28 6:47 ` Minchan Kim
2018-03-28 7:18 ` Martijn Coenen
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