On Mon, 25 May 2009 14:51:32 +0200
Stanislaw Gruszka [off-list ref] wrote:

On Mon, 25 May 2009 14:32:14 +0200 (CEST)
Thomas Gleixner [off-list ref] wrote:

quoted

On Mon, 25 May 2009, Stanislaw Gruszka wrote:

quoted

@@ -904,6 +905,7 @@ void __init time_init(void)
 	tb_ticks_per_usec = ppc_tb_freq / 1000000;
 	tb_to_us = mulhwu_scale_factor(ppc_tb_freq, 1000000);
 	calc_cputime_factors();
+	cputime_one = jiffies_to_cputime(1);

  1) The variable name is misleading.

What about cputime_one_jiffy ?

quoted

  2) The patch breaks all powerpc platforms which have
  CONFIG_VIRT_CPU_ACCOUNTING=n and ia64 with
  CONFIG_VIRT_CPU_ACCOUNTING=y

Stupid me, in asm-generic/cputime.h should be 
#define cputime_one jiffies_to_cputime(1)

Hmmm, I'm confused. Perhaps I missed something, but I think patch was ok.
For powerpc and ia64 and CONFIG_VIRT_CPU_ACCOUNTING=n definitions from
asm-generic/cputime.h where used. In this file was:

#define cputime_one (1UL) 

and that correct as jiffies_to_cputime(x) is just (x)

For CONFIG_VIRT_CPU_ACCOUTING=y:
- For powerpc additional variable was  declared and computed in
  initialization  time. Declaration of was in __KERENEL__ scope.
- For ia64: cputime_one was defined as jiffies_to_cputime(1)

Anyway I didn't try to even compile the patch on other architectures than x86.
Of cource I will test my patch, but first I would like to know what You think?
Does we really need such optimization (because before usage of
jiffies_to_cputime(1) was just fine) ?

Cheers
Stanislaw