Le Tuesday 13 Dec 2016 à 09:47:30 (+0800), Huang, Ying a écrit : > Hi, Vincent, > > Vincent Guittot writes: > > > Hi Ying, > > > > On 12 December 2016 at 06:43, kernel test robot > > wrote: > >> Greeting, > >> > >> FYI, we noticed a 149% regression of ftq.noise.50% due to commit: > >> > >> > >> commit: 4e5160766fcc9f41bbd38bac11f92dce993644aa ("sched/fair: Propagate asynchrous detach") > >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > >> > >> in testcase: ftq > >> on test machine: 8 threads Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 8G memory > >> with following parameters: > >> > >> nr_task: 100% > >> samples: 6000ss > >> test: cache > >> freq: 20 > >> cpufreq_governor: powersave > > > > Why using powersave ? Are you testing every governors ? > > We will test performance and powersave governor for FTQ. Ok thanks > > >> > >> test-description: The FTQ benchmarks measure hardware and software interference or 'noise' on a node from the applications perspective. > >> test-url: https://github.com/rminnich/ftq > > > > It's a bit difficult to understand exactly what is measured and what > > is ftq.noise.50% because this result is not part of the bench which > > seems to only record a log of data in a file and ftq.noise.50% seems > > to be lkp specific > > Yes. FTQ itself has no noise statistics builtin, although it is an OS > noise benchmark. ftq.noise.50% is calculated as below: > > There is a score for every sample of ftq. The lower the score, the > higher the noises. ftq.noise.50% is the number (per 1000000 samples) of > samples whose score is less than 50% of the mean score. > ok so IIUC we have moved from 0.03% to 0.11% for ftq.noise.50% I have not been able to reproduce the regression on the different system that I have access to so I can only guess the root cause of the regression. Could it be possible to test if the patch below fix the regression ? --- kernel/sched/fair.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 090a9bb..8efa113 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3138,6 +3138,31 @@ static inline int propagate_entity_load_avg(struct sched_entity *se) return 1; } +/* Check if we need to update the load and the utilization of a group_entity */ +static inline bool skip_blocked_update(struct sched_entity *se) +{ + struct cfs_rq *gcfs_rq = group_cfs_rq(se); + + /* + * If sched_entity still have not null load or utilization, we have to + * decay it. + */ + if (se->avg.load_avg || se->avg.util_avg) + return false; + + /* + * If there is a pending propagation, we have to update the load and + * the utilizaion of the sched_entity + */ + if (gcfs_rq->propagate_avg) + return false; + + /* + * Other wise, the load and the utilizaiton of the sched_entity is + * already null so it will be a waste of time to try to decay it + */ + return true; +} #else /* CONFIG_FAIR_GROUP_SCHED */ static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {} @@ -6858,6 +6883,7 @@ static void update_blocked_averages(int cpu) { struct rq *rq = cpu_rq(cpu); struct cfs_rq *cfs_rq; + struct sched_entity *se; unsigned long flags; raw_spin_lock_irqsave(&rq->lock, flags); @@ -6876,7 +6902,8 @@ static void update_blocked_averages(int cpu) update_tg_load_avg(cfs_rq, 0); /* Propagate pending load changes to the parent */ - if (cfs_rq->tg->se[cpu]) + se = cfs_rq->tg->se[cpu]; + if (se && !skip_blocked_update(se)) update_load_avg(cfs_rq->tg->se[cpu], 0); } raw_spin_unlock_irqrestore(&rq->lock, flags); -- 2.7.4 Thanks > Best Regards, > Huang, Ying > > > I have tried to reproduce the lkp test on a debian jessie then a > > ubuntu server 16.10 but lkp doesn't seems to install cleanly as there > > are some errors: > > > > sudo bin/lkp run job.yaml > > IPMI BMC is not supported on this machine, skip bmc-watchdog setup! > > 2016-12-12 13:58:39 ./ftq_cache -f 20 -n 6000 -t 8 -a 524288 > > Start 5088418680237 end 5438443372098 elapsed 350024691861 > > cyclestart 14236344834332 cycleend 15214154208877 elapsed 977809374545 > > Avg Cycles(ticks) per ns. is 2.793544; nspercycle is 0.357968 > > Pre-computed ticks per ns: 2.793541 > > Sample frequency is 20.000000 > > ticks per ns 2.79354 > > chown: utilisateur incorrect: «lkp.lkp» > > chown: utilisateur incorrect: «lkp.lkp» > > wait for background monitors: 9405 9407 oom-killer nfs-hang > > curl: (6) Could not resolve host: ftq.time > > > > > >> > >> In addition to that, the commit also has significant impact on the following tests: > >> > >> +------------------+--------------------------------------------------------------------------------+ > >> | testcase: change | unixbench: unixbench.score 2.7% improvement | > >> | test machine | 4 threads Intel(R) Core(TM) i3-3220 CPU @ 3.30GHz with 4G memory | > >> | test parameters | cpufreq_governor=performance | > >> | | nr_task=100% | > >> | | runtime=300s | > >> | | test=execl | > >> +------------------+--------------------------------------------------------------------------------+ > >> > >> > >> Details are as below: > >> --------------------------------------------------------------------------------------------------> > >> > >> > >> To reproduce: > >> > >> git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git > >> cd lkp-tests > >> bin/lkp install job.yaml # job file is attached in this email > >> bin/lkp run job.yaml > >> > >> testcase/path_params/tbox_group/run: ftq/100%-6000ss-cache-20-powersave/lkp-hsw-d01 > >> > >> 09a43ace1f986b00 4e5160766fcc9f41bbd38bac11 > >> ---------------- -------------------------- > >> %stddev change %stddev > >> \ | \ > >> 305 ± 30% 260% 1100 ± 14% ftq.noise.75% > >> 1386 ± 19% 149% 3457 ± 7% ftq.noise.50% > >> 2148 ± 11% 98% 4257 ± 4% ftq.noise.25% > >> 3963589 3898578 ftq.time.involuntary_context_switches > >> > >> > >> > >> ftq.noise.50_ > >> > >> 4000 ++------------O------------------------------------------------------+ > >> | O O | > >> 3500 ++ O O O O O O O > >> | O O O O O O O O O O O O O O | > >> O O O O O | > >> 3000 ++ O | > >> | O | > >> 2500 ++ | > >> | | > >> 2000 ++ | > >> | * .* | > >> | + : * * * + | > >> 1500 ++ + : + + + + : + .* | > >> |.* *. + * *.. : * + | > >> 1000 *+-------*-----------*----------*------------------------------------+ > >> > >> [*] bisect-good sample > >> [O] bisect-bad sample > >> > >> > >> Disclaimer: > >> Results have been estimated based on internal Intel analysis and are provided > >> for informational purposes only. Any difference in system hardware or software > >> design or configuration may affect actual performance. > >> > >> > >> Thanks, > >> Ying Huang > > _______________________________________________ > > LKP mailing list > > LKP@lists.01.org > > https://lists.01.org/mailman/listinfo/lkp