| Date | Mon, 1 Dec 2014 15:14:02 +0100 | From | Martin Schwidefsky <> | Subject | Re: [RFC PATCH 07/30] cputime: Convert kcpustat to nsecs |
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On Fri, 28 Nov 2014 19:23:37 +0100 Frederic Weisbecker <fweisbec@gmail.com> wrote:
> Kernel cpu stats are stored in cputime_t which is an architecture > defined type, and hence a bit opaque and requiring accessors and mutators > for any operation. > > Converting them to nsecs simplifies the code a little bit.
Quite honestly I do not see much of an improvement here, on set of functions (cputime_to_xxx) gets replaced by another (nsecs_to_xxx).
On the contrary for s390 I see a degradation, consider a hunk like this:
> @@ -128,9 +128,9 @@ static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall) > > idle_time = cur_wall_time - busy_time; > if (wall) > - *wall = cputime_to_usecs(cur_wall_time); > + *wall = div_u64(cur_wall_time, NSEC_PER_USEC); > > - return cputime_to_usecs(idle_time); > + return div_u64(idle_time, NSEC_PER_USEC); > } > > u64 get_cpu_idle_time(unsigned int cpu, u64 *wall, int io_busy)
For s390 cputime_to_usecs is a shift, with the new code we now have a division. Fortunately this is in a piece of code that s390 does not use..
-- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
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