[Linux-Xtensa] Re: sched_clock always 0 and no process time accounting with 3.11-rc1
Russell King - ARM Linux
linux at arm.linux.org.uk
Wed Jul 17 11:24:44 EDT 2013
On Wed, Jul 17, 2013 at 08:15:08AM -0700, Marc Gauthier wrote:
> Hi Baruch,
> On 2013-07-16, at 11:19 PM, Baruch Siach <baruch at tkos.co.il> wrote:
> > - sched_clock_mask = (1 << bits) - 1;
> > + sched_clock_mask = (1ULL << bits) - 1;
> Might it be more efficient to use:
> sched_clock_mask = 0xffffffff >> (32 - bits);
> to avoid using 64 bit ints?
> (assuming bits > 0, didn't check)
bits being 0 would be rather silly (it implies a mask of zero, and therefore
no bits available for the clock.) We could modify the BUG_ON() above to
make that point, or add it as commentry against the function.
Given that, and that sched_clock_mask is a u32, then I agree with you - the
above would be a better way to do this. Personally, I'd suggest ~0u rather
than 0xffffffff because its less typing.
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