Re: [PATCH] mm: slab.h: use ilog2() in kmalloc_index()

From	Christoph Lameter <cl@linux.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mm: slab.h: use ilog2() in kmalloc_index()
Date	2016-06-22 15:30 +0200
Message-ID	<rMQoa-41d-27@gated-at.bofh.it> (permalink)
References	<rMh74-6ol-41@gated-at.bofh.it> <rMC1Q-3dH-13@gated-at.bofh.it> <rMQoa-41d-29@gated-at.bofh.it>
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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.

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[PATCH] mm: slab.h: use ilog2() in kmalloc_index() Yury Norov <yury.norov@gmail.com> - 2016-06-21 01:50 +0200
  Re: [PATCH] mm: slab.h: use ilog2() in kmalloc_index() Andrew Morton <akpm@linux-foundation.org> - 2016-06-22 00:10 +0200
    Re: [PATCH] mm: slab.h: use ilog2() in kmalloc_index() Christoph Lameter <cl@linux.com> - 2016-06-22 15:30 +0200

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