| From | "Vaittinen, Matti" <> | Subject | Re: [PATCH v3 00/54] lib/bitmap: optimize bitmap_weight() usage | Date | Wed, 26 Jan 2022 07:30:03 +0000 |
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On 1/23/22 20:38, Yury Norov wrote: > In many cases people use bitmap_weight()-based functions to compare > the result against a number of expression: > > if (cpumask_weight(mask) > 1) > do_something(); > > This may take considerable amount of time on many-cpus machines because > cpumask_weight() will traverse every word of underlying cpumask > unconditionally. > > We can significantly improve on it for many real cases if stop traversing > the mask as soon as we count cpus to any number greater than 1: > > if (cpumask_weight_gt(mask, 1)) > do_something();
I guess I am part of the recipient list because I did the original suggestion of adding the single_bit_set()?
If this is the case - well, I do like this series. Overall it looks good to me - but I for sure did not go through all the changes in detail ;) If there is some other reason to loop me in (Eg, if someone expects me to take a more specific look on something) - please give me a nudge.
Best Regards -- Matti Vaittinen
-- The Linux Kernel guy at ROHM Semiconductors
Matti Vaittinen, Linux device drivers ROHM Semiconductors, Finland SWDC Kiviharjunlenkki 1E 90220 OULU FINLAND
~~ this year is the year of a signature writers block ~~
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