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    SubjectRe: [PATCH 2/2] kselftests: timers: Reduce default runtime on inconsistency-check and set-timer-lat
    On 03/26/2015 10:20 AM, John Stultz wrote:
    > On Thu, Mar 26, 2015 at 4:32 AM, Prarit Bhargava <prarit@redhat.com> wrote:
    >> On 03/25/2015 07:44 PM, John Stultz wrote:
    >>> For the default run_timers target, the timers tests takes the
    >>> majority of kselftests runtime.
    >>>
    >>> So this patch reduces the default runtime for inconsistentcy-check
    >>> and set-timer-lat, which reduced the runtime almost in half.
    >>>
    >>> Before: 11m48.629s
    >>> After: 6m47.723s
    >>>
    >>> Cc: Shuah Khan <shuahkh@osg.samsung.com>
    >>> Cc: Prarit Bhargava <prarit@redhat.com>
    >>> Cc: Thomas Gleixner <tglx@linutronix.de>
    >>> Cc: Richard Cochran <richardcochran@gmail.com>
    >>> Signed-off-by: John Stultz <john.stultz@linaro.org>
    >>> Signed-off-by: John Stultz <john.stultz@linaro.org>

    Same duplicate signature warning on this, no need to re-send.
    I will fix it when I apply the patch.

    -- Shuah
    >>> ---
    >>> tools/testing/selftests/timers/inconsistency-check.c | 2 +-
    >>> tools/testing/selftests/timers/set-timer-lat.c | 2 +-
    >>> 2 files changed, 2 insertions(+), 2 deletions(-)
    >>>
    >>> diff --git a/tools/testing/selftests/timers/inconsistency-check.c b/tools/testing/selftests/timers/inconsistency-check.c
    >>> index 578e423a..caf1bc9 100644
    >>> --- a/tools/testing/selftests/timers/inconsistency-check.c
    >>> +++ b/tools/testing/selftests/timers/inconsistency-check.c
    >>> @@ -166,7 +166,7 @@ int main(int argc, char *argv[])
    >>> int clockid, opt;
    >>> int userclock = CLOCK_REALTIME;
    >>> int maxclocks = NR_CLOCKIDS;
    >>> - int runtime = 30;
    >>> + int runtime = 10;
    >>> struct timespec ts;
    >>>
    >>
    >> Oops ... left everyone off :)
    >>
    >> What was the reason that this was originally 30? Or was that overkill?
    >
    > So time inconsistencies (when they manifest, which ideally is never)
    > can be fairly rare events. In the past we've seen them due to cpu TSC
    > skew and drift, which requires enough scheduler noise to pop the
    > process around between cores enough to notice, and enough system
    > runtime for the TSCs to drift far enough apart.. Or we've had tiny
    > accumulation bugs in update_wall_time which requires the right phase
    > in the error accumulation to align with an irq. So the consistency
    > test has always been a long running test (originally I'd run it
    > overnight), and the 30sec interval here was added just so there was
    > some "long enough" interval that wasn't too painful for me to test
    > submitted patches with. Now that more folks are using it (and they
    > likely care less), we can cut it down further to avoid making test
    > runs too onerous.
    >
    > Now, a patch might badly break things and it would be immediately
    > obvious to the test that something is wrong, so a quick check isn't
    > worthless, but it just doesn't instill that much confidence from me.
    >
    > I think as the kselftests grow, we'll have more "types" of test
    > targets to run (quick, long, stress, etc), and we can scale the time
    > in those tests accordingly. But the default should probably lean
    > towards the short side.
    >

    Right. I am working on adding support for quick, long etc. The goal
    for quick (default) mode is to complete the test runs in 15-20 minutes
    to make it easier for developers make it part of the work-flow.

    thanks,
    -- Shuah

    --
    Shuah Khan
    Sr. Linux Kernel Developer
    Open Source Innovation Group
    Samsung Research America (Silicon Valley)
    shuahkh@osg.samsung.com | (970) 217-8978


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