On Tuesday 14 November 2006 10:41, Andrew Morton wrote:
> Presently at
>
> http://userweb.kernel.org/~akpm/2.6.19-rc5-mm2/
>
> and will appear later at
>
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.19-rc5/2.
>6.19-rc5-mm2/
Hi all
I noticed a slowdown (3%) on a io micro-benchmark on my machine with
2.6.19-rc5-mm2
It appears time-uninline-jiffiesh.patch is sub-optimal at least for current
compilers (tested gcc-4.0.4 here)
May I suggest :
1) make sure jiffies_to_usecs() is defined before being used in
timespec_trunc() : Compiler will just optimize away not *needed* code.
OR :
2) Revert to inline versions of four functions jiffies_to_msecs(),
jiffies_to_usecs(), msecs_to_jiffies() and usecs_to_jiffies() .
IMHO there is litle gain to call a function just to perform so basic
arithmetics, that sometime compiler can perform at compilation time.
OR
3) replace
(jiffies_to_usecs(1) * 1000)
by
(NSEC_PER_SEC / HZ)
With current patch, timespec_trunc() is not anymore a tail function.
struct timespec timespec_trunc(struct timespec t, unsigned gran)
{
if (gran <= jiffies_to_usecs(1) * 1000) {
Much better here to have :
if (gran < SOME_CONSTANT)
Thank you
Eric
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