On 25.11.18 18:14, Philippe Gerum wrote:
On 11/21/18 5:59 PM, Jan Kiszka wrote:
If we change the quota value of thread group, we should take its already
consumed time during the current cycle into account. So far, we refilled
the budget blindly, which could have given the group an uncontrolled
"peak".
This commit first update the run_budget_ns of an active group and kills
its limit timer. Then it refills run_budget_ns only with the remaining
budget of the current cycle, taking the new quota as limit.
Accumulated credits are still dropped - not worth to deal with their
complexity in this scenario.
Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
---
Philippe, review would be appreciated.
Looks good.
Thanks. Applied to next now.
I'm still struggling with writing a good test case for that.
Absolutely untested, but what about doing this: calibrate some number
crunching loop to have it running for a given time you would use as the
initial quota value (e.g. 1s). Then,
. set the initial quota value
. run a test loop for 2/3 of the iterations spent in the calibration loop,
. decrease the initial quota value by half
. re-run the test loop, it should not have run more than half of the
calibrated iterations (+/- some error margin and fluctuations). A broken
quota implementation would have allowed 2/3 if IIUC.
I think the difference was only visible in the cycle of the adjustment. It
should have worked fine again on the next, clean round.
Checking for the actual number of iterations performed during the second
run could be done from a low priority thread which resumes when the test
runner is dequeued as the quota expires.
Both the test runner and the checker should be pinned on the same CPU.
With QUOTA_PERIOD larger and not too close to the initial quota value,
this should leave enough time for the low priority thread to check the
result.
I will think about that. It's annoying when tests turn out to be as complex - if
not more - as the actual code they test.
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
