lkml.org 
[lkml]   [2006]   [Aug]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [patch 1/3] add basic accounting fields to taskstats
    Balbir Singh wrote:
    > Jay Lan wrote:
    >> Jay Lan wrote:
    >>
    >> [snip]
    >>
    >>>>
    >>>>
    >>>>> + /* Each process gets a minimum of a half tick cpu time */
    >>>>> + if ((stats->ac_utime == 0) && (stats->ac_stime == 0)) {
    >>>>> + stats->ac_stime = USEC_PER_TICK/2;
    >>>>> + }
    >>>>> +
    >>>>
    >>>>
    >>>>
    >>>> This is confusing. Half tick does not make any sense from the
    >>>> scheduler view point (or am I missing something?), so why
    >>>> return half a tick to the user.
    >>>
    >>>
    >>> It must be inherited from old code dated back to Cray UNICOS.
    >>> I do not know if bad thing can happen if both utime and stime
    >>> are less than 1 usec... I guess not. But i agree that
    >>> half a tick does not make sense. To play safe, we can change
    >>> it to 1 usec if both utime and stime are sub microsecond.
    >>> What do you think?
    >>
    >> Hi Balbir,
    >>
    >> I figured this out. The tsk->stime (and utime as well) are
    >> charged by 1 tick (or cputime) from the timer interrupt handler
    >> through update_process_times->account_{user,system}_time.
    >>
    >> The clock resolution is a tick. Any short process less than
    >> 1 tick will the counter being 0. It can be from 0 to 0.99999...
    >> tick. A half tick is the average value.
    >>
    >
    > But the scheduling happens in the granularity of a tick, so the
    > minimum each task gets is a tick.
    >
    >> I think it makes more sense to assign a half tick than assign
    >> 1 usec to the stime. What do you think? Certainly the code need
    >> better explanation.
    >>
    >
    > Can't we leave these values as zero in case both stime and utime are
    > zero.

    Yes, i will leave them as zero in this case.

    Regards,
    - jay

    >
    >
    >> Regards,
    >> - jay
    >>
    >>
    >> [snip]
    >
    >

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-08-08 18:43    [W:0.023 / U:63.336 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site