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

Tvrtko Ursulin
2023-06-26T09:03:00Z

On 20/06/2023 14:23, Ira Weiny wrote:
> Sumitra Sharma wrote:
>> 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?
>
> Shorthand for 'nitpicking'.
>
> "giving too much attention to details that are not important, especially
> as a way of criticizing: "
>
> - https://dictionary.cambridge.org/dictionary/english/nitpicking
>
> Via email this is a way for authors of an email to indicate something is
> technically wrong but while nicely acknowledging that it is not very
> significant and could be seen as overly critical.
>
> For this particular comment I'm showing something to pay attention to next
> time but that was not a big deal this time around.
>
>>
>> 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?
>>
>
> Based on this response[*] from Tvrtko I think this version can move
> through without a v3.
>
> Thanks!
> Ira
>
> [*] https://lore.kernel.org/all/bcb0a1d2-cd4d-a56f-1ee6-7ccfdd2f7b38@linux.intel.com/
>
> <quote>
> Thanks all! I'll just re-send the patch for our CI, since it didn't get
> picked up automatically (stuck in moderation perhaps), with all r-b tags
> added and extra line space removed and merge it if results will be green.
>
> Regards,
>
> Tvrtko
> </quote>

Pushed to drm-intel-gt-next, thanks for the patch and reviews!

Regards,

Tvrtko