Messages in this thread |  | | Date | Sat, 23 Apr 2022 18:02:48 +0200 | Subject | Re: [PATCH 3/3] binder: Use kmap_local_page() in binder_alloc_get_page() | From | Christophe JAILLET <> |
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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;
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