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SubjectRe: [Patch 1/4] Delay accounting: Initialization

On Nov 14, 2005, at 11:35 PM, Shailabh Nagar wrote:

> +/* because of hardware timer drifts in SMPs and task continue on
> different cpu
> + * then where the start_ts was taken there is a possibility that
> + * end_ts < start_ts by some usecs. In this case we ignore the diff
> + * and add nothing to the total.

Curious as to when would this occur. Probably for tasks running on a
SMP machine for a very short period of time (timer drift should not
be hopefully that high) and switching CPUs in that short period of time?

> +config DELAY_ACCT

better names?

> @@ -813,6 +821,9 @@ struct task_struct {
> int cpuset_mems_generation;
> #endif
> atomic_t fs_excl; /* holding fs exclusive resources */
> + struct task_delay_info delays;
> +#endif
> };

Does this mean, whether or not the per task delay accounting is used,
we have a constant overhead of sizeof(spinlock_t) + 2*sizeof
(uint32_t) + 2* sizeof(uint64_t) bytes going into the struct
task_struct?. Is it possible/beneficial to use struct task_delay_info
*delays instead and allocate it if task wants to use the information?

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