Messages in this thread | | | Date | Mon, 29 Aug 2022 12:36:21 +0900 | From | Hyeonggon Yoo <> | Subject | Re: [PATCH] mm: simplify size2index conversion of __kmalloc_index |
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On Mon, Aug 29, 2022 at 04:11:04AM +0100, Matthew Wilcox wrote: > On Sun, Aug 28, 2022 at 11:14:48PM +0800, Dawei Li wrote: > > Current size2index is implemented by one to one hardcode mapping, > > which can be improved by order_base_2(). > > Must be careful to not violate compile-time optimization rule. > > This patch has been NACKed before (when submitted by other people).
Hmm right. https://lkml.iu.edu/hypermail/linux/kernel/1606.2/05402.html
Christoph Lameter wrote: > On Wed, 22 Jun 2016, Yury Norov wrote: > > There will be no fls() for constant at runtime because ilog2() calculates > > constant values at compile-time as well. From this point of view, > > this patch removes code duplication, as we already have compile-time > > log() calculation in kernel, and should re-use it whenever possible.\
> The reason not to use ilog there was that the constant folding did not > work correctly with one or the other architectures/compilers. If you want > to do this then please verify that all arches reliably do produce a > constant there.
Can we re-evaluate this?
-- Thanks, Hyeonggon
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