Re: [Intel-gfx] [PATCH v2] drm/i915: Replace kmap() with kmap_local_page()

Sumitra Sharma
2023-06-20T18:28:36Z

On Sun, Jun 18, 2023 at 11:11:08AM -0700, Ira Weiny wrote:
> Sumitra Sharma wrote:
> > kmap() has been deprecated in favor of the kmap_local_page()
> > due to high cost, restricted mapping space, the overhead of a
> > global lock for synchronization, and making the process sleep
> > in the absence of free slots.
> >
> > kmap_local_page() is faster than kmap() and offers thread-local
> > and CPU-local mappings, take pagefaults in a local kmap region
> > and preserves preemption by saving the mappings of outgoing tasks
> > and restoring those of the incoming one during a context switch.
> >
> > The mapping is kept thread local in the function
> > “i915_vma_coredump_create” in i915_gpu_error.c
> >
> > Therefore, replace kmap() with kmap_local_page().
> >
> > Suggested-by: Ira Weiny <ira.weiny@intel.com>
> >
>
> NIT: No need for the line break between Suggested-by and your signed off line.
>

Hi Ira,

What does NIT stand for?

Thank you. I will take care about the line breaks.

> > Signed-off-by: Sumitra Sharma <sumitraartsy@gmail.com>
> > ---
> >
> > Changes in v2:
> > - Replace kmap() with kmap_local_page().
>
> Generally it is customary to attribute a change like this to those who
> suggested it in a V1 review.
>
> For example:
>
> - Tvrtko/Thomas: Use kmap_local_page() instead of page_address()
>
> Also I don't see Thomas on the new email list. Since he took the time to
> review V1 he might want to check this version out. I've added him to the
> 'To:' list.
>
> Also a link to V1 is nice. B4 formats it like this:
>
> - Link to v1: https://lore.kernel.org/all/20230614123556.GA381200@sumitra.com/
>
> All that said the code looks good to me. So with the above changes.
>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
>

I have noted down the points mentioned above. Thank you again.

I am not supposed to create another version of this patch for
adding the above mentions, as you and Thomas both gave this patch
a reviewed-by tag. Right?

Thanks & regards
Sumitra

PS: I am new to the open source vocabulary terms.

> > - Change commit subject and message.
> >
> > drivers/gpu/drm/i915/i915_gpu_error.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> > index f020c0086fbc..bc41500eedf5 100644
> > --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> > +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> > @@ -1164,9 +1164,9 @@ i915_vma_coredump_create(const struct intel_gt *gt,
> >
> > drm_clflush_pages(&page, 1);
> >
> > - s = kmap(page);
> > + s = kmap_local_page(page);
> > ret = compress_page(compress, s, dst, false);
> > - kunmap(page);
> > + kunmap_local(s);
> >
> > drm_clflush_pages(&page, 1);
> >
> > --
> > 2.25.1
> >
>
>