On Thu, 26 Oct 2006, David Rientjes wrote:
On Fri, 27 Oct 2006, Martin Tostrup Setek wrote:
from: Martin T. Setek <[email protected]>
cpu_count in struct taskstats should be the same as the corresponding (third)
value found in /proc/<pid>/schedstat
I disagree in favor of Documentation/accounting/taskstats-struct.txt.
cpu_count is the number of delay values recorded, so accumulating them is
appropriate.
Perhaps I'm mistaken, but the code accumulates the value it
finds in sched_info.pcnt in the task_struct. Now, in sched.h I found this:
struct sched_info {
/* cumulative counters */
unsigned long cpu_time, /* time spent on the cpu */
run_delay, /* time spent waiting on a runqueue */
pcnt; /* # of timeslices run on this cpu */
The comment says that these counters are cumulative... The code that
updates them (sched.c: sched_info_arrive()), does accumulate them.
In include/linux/taskstats.h, I found:
* xxx_count is the number of delay values recorded
* xxx_delay_total is the corresponding cumulative delay in nanoseconds
I interpret these comments as saying that:
cpu_delay should be the total number of nanoseconds a task has been
waiting in a runqueue for a CPU, and cpu_count is equal to the number of
times the task got the CPU (or waited for it). If so, then the code
updates taskstats.cpu_delay_total incorrectly too (which my patch didn't
fix).
If not, then the comments in taskstats.h are very confusing....
Martin
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