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
