* [PATCH 0/3] binder: Use kmap_local_page() in binder_alloc.c
@ 2022-04-23 10:24 Fabio M. De Francesco
2022-04-23 10:24 ` [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf() Fabio M. De Francesco
` (2 more replies)
0 siblings, 3 replies; 11+ messages in thread
From: Fabio M. De Francesco @ 2022-04-23 10:24 UTC (permalink / raw)
To: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
Cc: Fabio M. De Francesco
Use kmap_local_page() in binder_alloc.c because kmap() and kmap_atomic()
are being deprecated and kmap_local_page is preferred where it is feasible.
With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Furthermore, the mapping can be acquired from any
context, including interrupts.
Fabio M. De Francesco (3):
binder: Use memset_page() in binder_alloc_clear_buf()
binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer()
binder: Use kmap_local_page() in binder_alloc_get_page()
drivers/android/binder_alloc.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
--
2.34.1
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf()
2022-04-23 10:24 [PATCH 0/3] binder: Use kmap_local_page() in binder_alloc.c Fabio M. De Francesco
@ 2022-04-23 10:24 ` Fabio M. De Francesco
2022-04-23 15:43 ` Todd Kjos
2022-04-23 10:24 ` [PATCH 2/3] binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer() Fabio M. De Francesco
2022-04-23 10:24 ` [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page() Fabio M. De Francesco
2 siblings, 1 reply; 11+ messages in thread
From: Fabio M. De Francesco @ 2022-04-23 10:24 UTC (permalink / raw)
To: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
Cc: Fabio M. De Francesco
The use of kmap() is being deprecated in favor of kmap_local_page()
where it is feasible. With kmap_local_page(), the mapping is per
thread, CPU local and not globally visible.
binder_alloc_clear_buf() is a function where the use of kmap_local_page()
in place of kmap() is correctly suited because the mapping is local to the
thread.
Therefore, use kmap_local_page() / kunmap_local() but, instead of open
coding these two functions and adding a memset() of the virtual address
of the mapping, prefer memset_page().
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
drivers/android/binder_alloc.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 2ac1008a5f39..0b3f2f569053 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1175,14 +1175,11 @@ static void binder_alloc_clear_buf(struct binder_alloc *alloc,
unsigned long size;
struct page *page;
pgoff_t pgoff;
- void *kptr;
page = binder_alloc_get_page(alloc, buffer,
buffer_offset, &pgoff);
size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
- kptr = kmap(page) + pgoff;
- memset(kptr, 0, size);
- kunmap(page);
+ memset_page(page, pgoff, 0, size);
bytes -= size;
buffer_offset += size;
}
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH 2/3] binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer()
2022-04-23 10:24 [PATCH 0/3] binder: Use kmap_local_page() in binder_alloc.c Fabio M. De Francesco
2022-04-23 10:24 ` [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf() Fabio M. De Francesco
@ 2022-04-23 10:24 ` Fabio M. De Francesco
2022-04-23 15:43 ` Todd Kjos
2022-04-23 10:24 ` [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page() Fabio M. De Francesco
2 siblings, 1 reply; 11+ messages in thread
From: Fabio M. De Francesco @ 2022-04-23 10:24 UTC (permalink / raw)
To: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
Cc: Fabio M. De Francesco
The use of kmap() is being deprecated in favor of kmap_local_page()
where it is feasible. With kmap_local_page(), the mapping is per
thread, CPU local and not globally visible.
binder_alloc_copy_user_to_buffer() is a function where the use of
kmap_local_page() in place of kmap() is correctly suited because
the mapping is local to the thread.
Therefore, use kmap_local_page() / kunmap_local().
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
drivers/android/binder_alloc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 0b3f2f569053..0875c463c002 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1217,9 +1217,9 @@ binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
page = binder_alloc_get_page(alloc, buffer,
buffer_offset, &pgoff);
size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
- kptr = kmap(page) + pgoff;
+ kptr = kmap_local_page(page) + pgoff;
ret = copy_from_user(kptr, from, size);
- kunmap(page);
+ kunmap_local(kptr);
if (ret)
return bytes - size + ret;
bytes -= size;
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
2022-04-23 10:24 [PATCH 0/3] binder: Use kmap_local_page() in binder_alloc.c Fabio M. De Francesco
2022-04-23 10:24 ` [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf() Fabio M. De Francesco
2022-04-23 10:24 ` [PATCH 2/3] binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer() Fabio M. De Francesco
@ 2022-04-23 10:24 ` Fabio M. De Francesco
2022-04-23 15:44 ` Todd Kjos
2022-04-23 16:02 ` Christophe JAILLET
2 siblings, 2 replies; 11+ messages in thread
From: Fabio M. De Francesco @ 2022-04-23 10:24 UTC (permalink / raw)
To: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
Cc: Fabio M. De Francesco
The use of kmap_atomic() is being deprecated in favor of kmap_local_page()
where it is feasible. Each call of kmap_atomic() in the kernel creates
a non-preemptible section and disable pagefaults. This could be a source
of unwanted latency, so it should be only used if it is absolutely
required, otherwise kmap_local_page() should be preferred.
With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Furthermore, the mapping can be acquired from any context
(including interrupts).
Therefore, use kmap_local_page() / kunmap_local() in place of
kmap_atomic() / kunmap_atomic().
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---
drivers/android/binder_alloc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 0875c463c002..058595cc7ff0 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
page = binder_alloc_get_page(alloc, buffer,
buffer_offset, &pgoff);
size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
- base_ptr = kmap_atomic(page);
+ base_ptr = kmap_local_page(page);
tmpptr = base_ptr + pgoff;
if (to_buffer)
memcpy(tmpptr, ptr, size);
else
memcpy(ptr, tmpptr, size);
/*
- * kunmap_atomic() takes care of flushing the cache
+ * kunmap_local() takes care of flushing the cache
* if this device has VIVT cache arch
*/
- kunmap_atomic(base_ptr);
+ kunmap_local(base_ptr);
bytes -= size;
pgoff = 0;
ptr = ptr + size;
--
2.34.1
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf()
2022-04-23 10:24 ` [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf() Fabio M. De Francesco
@ 2022-04-23 15:43 ` Todd Kjos
0 siblings, 0 replies; 11+ messages in thread
From: Todd Kjos @ 2022-04-23 15:43 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
On Sat, Apr 23, 2022 at 3:24 AM Fabio M. De Francesco
<fmdefrancesco@gmail.com> wrote:
>
> The use of kmap() is being deprecated in favor of kmap_local_page()
> where it is feasible. With kmap_local_page(), the mapping is per
> thread, CPU local and not globally visible.
>
> binder_alloc_clear_buf() is a function where the use of kmap_local_page()
> in place of kmap() is correctly suited because the mapping is local to the
> thread.
>
> Therefore, use kmap_local_page() / kunmap_local() but, instead of open
> coding these two functions and adding a memset() of the virtual address
> of the mapping, prefer memset_page().
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Todd Kjos <tkjos@google.com>
> ---
> drivers/android/binder_alloc.c | 5 +----
> 1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 2ac1008a5f39..0b3f2f569053 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -1175,14 +1175,11 @@ static void binder_alloc_clear_buf(struct binder_alloc *alloc,
> unsigned long size;
> struct page *page;
> pgoff_t pgoff;
> - void *kptr;
>
> page = binder_alloc_get_page(alloc, buffer,
> buffer_offset, &pgoff);
> size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> - kptr = kmap(page) + pgoff;
> - memset(kptr, 0, size);
> - kunmap(page);
> + memset_page(page, pgoff, 0, size);
> bytes -= size;
> buffer_offset += size;
> }
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 2/3] binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer()
2022-04-23 10:24 ` [PATCH 2/3] binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer() Fabio M. De Francesco
@ 2022-04-23 15:43 ` Todd Kjos
0 siblings, 0 replies; 11+ messages in thread
From: Todd Kjos @ 2022-04-23 15:43 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
On Sat, Apr 23, 2022 at 3:24 AM Fabio M. De Francesco
<fmdefrancesco@gmail.com> wrote:
>
> The use of kmap() is being deprecated in favor of kmap_local_page()
> where it is feasible. With kmap_local_page(), the mapping is per
> thread, CPU local and not globally visible.
>
> binder_alloc_copy_user_to_buffer() is a function where the use of
> kmap_local_page() in place of kmap() is correctly suited because
> the mapping is local to the thread.
>
> Therefore, use kmap_local_page() / kunmap_local().
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Todd Kjos <tkjos@google.com>
> ---
> drivers/android/binder_alloc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 0b3f2f569053..0875c463c002 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -1217,9 +1217,9 @@ binder_alloc_copy_user_to_buffer(struct binder_alloc *alloc,
> page = binder_alloc_get_page(alloc, buffer,
> buffer_offset, &pgoff);
> size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> - kptr = kmap(page) + pgoff;
> + kptr = kmap_local_page(page) + pgoff;
> ret = copy_from_user(kptr, from, size);
> - kunmap(page);
> + kunmap_local(kptr);
> if (ret)
> return bytes - size + ret;
> bytes -= size;
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
2022-04-23 10:24 ` [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page() Fabio M. De Francesco
@ 2022-04-23 15:44 ` Todd Kjos
2022-04-23 16:02 ` Christophe JAILLET
1 sibling, 0 replies; 11+ messages in thread
From: Todd Kjos @ 2022-04-23 15:44 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Martijn Coenen, Joel Fernandes, Christian Brauner,
Hridya Valsaraju, Suren Baghdasaryan, Ira Weiny, linux-kernel
On Sat, Apr 23, 2022 at 3:24 AM Fabio M. De Francesco
<fmdefrancesco@gmail.com> wrote:
>
> The use of kmap_atomic() is being deprecated in favor of kmap_local_page()
> where it is feasible. Each call of kmap_atomic() in the kernel creates
> a non-preemptible section and disable pagefaults. This could be a source
> of unwanted latency, so it should be only used if it is absolutely
> required, otherwise kmap_local_page() should be preferred.
>
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible. Furthermore, the mapping can be acquired from any context
> (including interrupts).
>
> Therefore, use kmap_local_page() / kunmap_local() in place of
> kmap_atomic() / kunmap_atomic().
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Todd Kjos <tkjos@google.com>
> ---
> drivers/android/binder_alloc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 0875c463c002..058595cc7ff0 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
> page = binder_alloc_get_page(alloc, buffer,
> buffer_offset, &pgoff);
> size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> - base_ptr = kmap_atomic(page);
> + base_ptr = kmap_local_page(page);
> tmpptr = base_ptr + pgoff;
> if (to_buffer)
> memcpy(tmpptr, ptr, size);
> else
> memcpy(ptr, tmpptr, size);
> /*
> - * kunmap_atomic() takes care of flushing the cache
> + * kunmap_local() takes care of flushing the cache
> * if this device has VIVT cache arch
> */
> - kunmap_atomic(base_ptr);
> + kunmap_local(base_ptr);
> bytes -= size;
> pgoff = 0;
> ptr = ptr + size;
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
@ 2022-04-23 16:02 ` Christophe JAILLET
0 siblings, 0 replies; 11+ messages in thread
From: Christophe JAILLET @ 2022-04-23 16:02 UTC (permalink / raw)
To: Fabio M. De Francesco, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Martijn Coenen,
Joel Fernandes, Christian Brauner, Hridya Valsaraju,
Suren Baghdasaryan, Ira Weiny, linux-kernel
Hi,
Le 23/04/2022 à 12:24, Fabio M. De Francesco a écrit :
> The use of kmap_atomic() is being deprecated in favor of kmap_local_page()
> where it is feasible. Each call of kmap_atomic() in the kernel creates
> a non-preemptible section and disable pagefaults. This could be a source
> of unwanted latency, so it should be only used if it is absolutely
> required, otherwise kmap_local_page() should be preferred.
>
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible. Furthermore, the mapping can be acquired from any context
> (including interrupts).
>
> Therefore, use kmap_local_page() / kunmap_local() in place of
> kmap_atomic() / kunmap_atomic().
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> ---
> drivers/android/binder_alloc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 0875c463c002..058595cc7ff0 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
> page = binder_alloc_get_page(alloc, buffer,
> buffer_offset, &pgoff);
> size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> - base_ptr = kmap_atomic(page);
> + base_ptr = kmap_local_page(page);
> tmpptr = base_ptr + pgoff;
> if (to_buffer)
> memcpy(tmpptr, ptr, size);
> else
> memcpy(ptr, tmpptr, size);
in the same spirit as patch 1/3, memcpy_to_page() and memcpy_from_page()
looks good candidate to avoid code duplication.
Not checked in details, but looks mostly the same.
Just my 2c.
CJ
> /*
> - * kunmap_atomic() takes care of flushing the cache
> + * kunmap_local() takes care of flushing the cache
> * if this device has VIVT cache arch
> */
> - kunmap_atomic(base_ptr);
> + kunmap_local(base_ptr);
> bytes -= size;
> pgoff = 0;
> ptr = ptr + size;
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
@ 2022-04-23 16:02 ` Christophe JAILLET
0 siblings, 0 replies; 11+ messages in thread
From: Christophe JAILLET @ 2022-04-23 16:02 UTC (permalink / raw)
To: linux-kernel
Hi,
Le 23/04/2022 à 12:24, Fabio M. De Francesco a écrit :
> The use of kmap_atomic() is being deprecated in favor of kmap_local_page()
> where it is feasible. Each call of kmap_atomic() in the kernel creates
> a non-preemptible section and disable pagefaults. This could be a source
> of unwanted latency, so it should be only used if it is absolutely
> required, otherwise kmap_local_page() should be preferred.
>
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible. Furthermore, the mapping can be acquired from any context
> (including interrupts).
>
> Therefore, use kmap_local_page() / kunmap_local() in place of
> kmap_atomic() / kunmap_atomic().
>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> ---
> drivers/android/binder_alloc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> index 0875c463c002..058595cc7ff0 100644
> --- a/drivers/android/binder_alloc.c
> +++ b/drivers/android/binder_alloc.c
> @@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct binder_alloc *alloc,
> page = binder_alloc_get_page(alloc, buffer,
> buffer_offset, &pgoff);
> size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> - base_ptr = kmap_atomic(page);
> + base_ptr = kmap_local_page(page);
> tmpptr = base_ptr + pgoff;
> if (to_buffer)
> memcpy(tmpptr, ptr, size);
> else
> memcpy(ptr, tmpptr, size);
in the same spirit as patch 1/3, memcpy_to_page() and memcpy_from_page()
looks good candidate to avoid code duplication.
Not checked in details, but looks mostly the same.
Just my 2c.
CJ
> /*
> - * kunmap_atomic() takes care of flushing the cache
> + * kunmap_local() takes care of flushing the cache
> * if this device has VIVT cache arch
> */
> - kunmap_atomic(base_ptr);
> + kunmap_local(base_ptr);
> bytes -= size;
> pgoff = 0;
> ptr = ptr + size;
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
2022-04-23 16:02 ` Christophe JAILLET
(?)
@ 2022-04-24 9:39 ` Fabio M. De Francesco
2022-04-25 15:52 ` Todd Kjos
-1 siblings, 1 reply; 11+ messages in thread
From: Fabio M. De Francesco @ 2022-04-24 9:39 UTC (permalink / raw)
To: Todd Kjos, linux-kernel, Christophe JAILLET
Cc: Greg Kroah-Hartman, Arve Hjønnevåg, Martijn Coenen,
Joel Fernandes, Christian Brauner, Hridya Valsaraju,
Suren Baghdasaryan, Ira Weiny
On sabato 23 aprile 2022 18:02:48 CEST Christophe JAILLET wrote:
> Hi,
>
> Le 23/04/2022 à 12:24, Fabio M. De Francesco a écrit :
> > The use of kmap_atomic() is being deprecated in favor of
kmap_local_page()
> > where it is feasible. Each call of kmap_atomic() in the kernel creates
> > a non-preemptible section and disable pagefaults. This could be a
source
> > of unwanted latency, so it should be only used if it is absolutely
> > required, otherwise kmap_local_page() should be preferred.
> >
> > With kmap_local_page(), the mapping is per thread, CPU local and not
> > globally visible. Furthermore, the mapping can be acquired from any
context
> > (including interrupts).
> >
> > Therefore, use kmap_local_page() / kunmap_local() in place of
> > kmap_atomic() / kunmap_atomic().
> >
> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> > ---
> > drivers/android/binder_alloc.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/android/binder_alloc.c b/drivers/android/
binder_alloc.c
> > index 0875c463c002..058595cc7ff0 100644
> > --- a/drivers/android/binder_alloc.c
> > +++ b/drivers/android/binder_alloc.c
> > @@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct
binder_alloc *alloc,
> > page = binder_alloc_get_page(alloc, buffer,
> > buffer_offset,
&pgoff);
> > size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> > - base_ptr = kmap_atomic(page);
> > + base_ptr = kmap_local_page(page);
> > tmpptr = base_ptr + pgoff;
> > if (to_buffer)
> > memcpy(tmpptr, ptr, size);
> > else
> > memcpy(ptr, tmpptr, size);
>
> in the same spirit as patch 1/3, memcpy_to_page() and memcpy_from_page()
> looks good candidate to avoid code duplication.
Hello Christophe, Todd,
I had thought to use memcpy_to_page() and memcpy_from_page() (exactly as I
did in other conversions I have been working on during the latest couple of
weeks).
However, I decided to avoid to use them for I should also have deleted the
comment which is before "kunmap_local(base_ptr);".
I don't know how much Maintainers think it is necessary to make readers
notice that "kunmap_local() takes care of flushing the cache []" (exactly
as kunmap_atomic() does). Actually I'd delete that comment that looks
redundant and unnecessary to me, but I cannot know if Todd wants it to
remain there.
@Todd: Can you please say what you think about this topic? Should I leave
the patch as-is or I should use memcpy_{to,from}_page() and delete that
comment?
I won't send any v2 unless I have your confirmation.
Thanks,
Fabio
>
> Not checked in details, but looks mostly the same.
>
> Just my 2c.
>
> CJ
>
> > /*
> > - * kunmap_atomic() takes care of flushing the cache
> > + * kunmap_local() takes care of flushing the cache
> > * if this device has VIVT cache arch
> > */
> > - kunmap_atomic(base_ptr);
> > + kunmap_local(base_ptr);
> > bytes -= size;
> > pgoff = 0;
> > ptr = ptr + size;
>
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page()
2022-04-24 9:39 ` Fabio M. De Francesco
@ 2022-04-25 15:52 ` Todd Kjos
0 siblings, 0 replies; 11+ messages in thread
From: Todd Kjos @ 2022-04-25 15:52 UTC (permalink / raw)
To: Fabio M. De Francesco
Cc: Todd Kjos, linux-kernel, Christophe JAILLET, Greg Kroah-Hartman,
Arve Hjønnevåg, Martijn Coenen, Joel Fernandes,
Christian Brauner, Hridya Valsaraju, Suren Baghdasaryan,
Ira Weiny
On Sun, Apr 24, 2022 at 2:40 AM Fabio M. De Francesco
<fmdefrancesco@gmail.com> wrote:
>
> On sabato 23 aprile 2022 18:02:48 CEST Christophe JAILLET wrote:
> > Hi,
> >
> > Le 23/04/2022 à 12:24, Fabio M. De Francesco a écrit :
> > > The use of kmap_atomic() is being deprecated in favor of
> kmap_local_page()
> > > where it is feasible. Each call of kmap_atomic() in the kernel creates
> > > a non-preemptible section and disable pagefaults. This could be a
> source
> > > of unwanted latency, so it should be only used if it is absolutely
> > > required, otherwise kmap_local_page() should be preferred.
> > >
> > > With kmap_local_page(), the mapping is per thread, CPU local and not
> > > globally visible. Furthermore, the mapping can be acquired from any
> context
> > > (including interrupts).
> > >
> > > Therefore, use kmap_local_page() / kunmap_local() in place of
> > > kmap_atomic() / kunmap_atomic().
> > >
> > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> > > ---
> > > drivers/android/binder_alloc.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/android/binder_alloc.c b/drivers/android/
> binder_alloc.c
> > > index 0875c463c002..058595cc7ff0 100644
> > > --- a/drivers/android/binder_alloc.c
> > > +++ b/drivers/android/binder_alloc.c
> > > @@ -1250,17 +1250,17 @@ static int binder_alloc_do_buffer_copy(struct
> binder_alloc *alloc,
> > > page = binder_alloc_get_page(alloc, buffer,
> > > buffer_offset,
> &pgoff);
> > > size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
> > > - base_ptr = kmap_atomic(page);
> > > + base_ptr = kmap_local_page(page);
> > > tmpptr = base_ptr + pgoff;
> > > if (to_buffer)
> > > memcpy(tmpptr, ptr, size);
> > > else
> > > memcpy(ptr, tmpptr, size);
> >
> > in the same spirit as patch 1/3, memcpy_to_page() and memcpy_from_page()
> > looks good candidate to avoid code duplication.
>
> Hello Christophe, Todd,
>
> I had thought to use memcpy_to_page() and memcpy_from_page() (exactly as I
> did in other conversions I have been working on during the latest couple of
> weeks).
>
> However, I decided to avoid to use them for I should also have deleted the
> comment which is before "kunmap_local(base_ptr);".
>
> I don't know how much Maintainers think it is necessary to make readers
> notice that "kunmap_local() takes care of flushing the cache []" (exactly
> as kunmap_atomic() does). Actually I'd delete that comment that looks
> redundant and unnecessary to me, but I cannot know if Todd wants it to
> remain there.
>
> @Todd: Can you please say what you think about this topic? Should I leave
> the patch as-is or I should use memcpy_{to,from}_page() and delete that
> comment?
I'm fine with using memcpy_{to,from}_page() and removing the comment.
>
> I won't send any v2 unless I have your confirmation.
>
> Thanks,
>
> Fabio
>
> >
> > Not checked in details, but looks mostly the same.
> >
> > Just my 2c.
> >
> > CJ
> >
> > > /*
> > > - * kunmap_atomic() takes care of flushing the cache
> > > + * kunmap_local() takes care of flushing the cache
> > > * if this device has VIVT cache arch
> > > */
> > > - kunmap_atomic(base_ptr);
> > > + kunmap_local(base_ptr);
> > > bytes -= size;
> > > pgoff = 0;
> > > ptr = ptr + size;
> >
> >
>
>
>
>
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2022-04-25 15:52 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-23 10:24 [PATCH 0/3] binder: Use kmap_local_page() in binder_alloc.c Fabio M. De Francesco
2022-04-23 10:24 ` [PATCH 1/3] binder: Use memset_page() in binder_alloc_clear_buf() Fabio M. De Francesco
2022-04-23 15:43 ` Todd Kjos
2022-04-23 10:24 ` [PATCH 2/3] binder: Use kmap_local_page() in binder_alloc_copy_user_to_buffer() Fabio M. De Francesco
2022-04-23 15:43 ` Todd Kjos
2022-04-23 10:24 ` [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page() Fabio M. De Francesco
2022-04-23 15:44 ` Todd Kjos
2022-04-23 16:02 ` Christophe JAILLET
2022-04-23 16:02 ` Christophe JAILLET
2022-04-24 9:39 ` Fabio M. De Francesco
2022-04-25 15:52 ` Todd Kjos
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