Messages in this thread Patch in this message | | | Subject | Re: [LKP] [sched/fair] 6c8116c914: stress-ng.mmapfork.ops_per_sec -38.0% regression | From | Xing Zhengjun <> | Date | Fri, 12 Jun 2020 15:59:31 +0800 |
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Hi,
I test the regression, it still existed in v5.7. If you have any fix for it, please send it to me, I can verify it. Thanks.
========================================================================================= tbox_group/testcase/rootfs/kconfig/compiler/nr_threads/disk/sc_pid_max/testtime/class/cpufreq_governor/ucode: lkp-bdw-ep6/stress-ng/debian-x86_64-20191114.cgz/x86_64-rhel-7.6/gcc-7/100%/1HDD/4194304/1s/scheduler/performance/0xb000038
commit: e94f80f6c49020008e6fa0f3d4b806b8595d17d8 6c8116c914b65be5e4d6f66d69c8142eb0648c22 v5.7-rc3 v5.7
e94f80f6c4902000 6c8116c914b65be5e4d6f66d69c v5.7-rc3 v5.7 ---------------- --------------------------- --------------------------- --------------------------- %stddev %change %stddev %change %stddev %change %stddev \ | \ | \ | \ 21398 ± 7% +6.5% 22781 ± 2% -14.5% 18287 ± 4% -5.5% 20231 ± 14% stress-ng.clone.ops 819250 ± 5% -10.1% 736616 ± 8% +34.2% 1099410 ± 5% +41.2% 1156877 ± 3% stress-ng.futex.ops 818985 ± 5% -10.1% 736460 ± 8% +34.2% 1099487 ± 5% +41.2% 1156215 ± 3% stress-ng.futex.ops_per_sec 1551 ± 3% -3.4% 1498 ± 5% -9.5% 1404 ± 2% -4.6% 1480 ± 5% stress-ng.inotify.ops 1547 ± 3% -3.5% 1492 ± 5% -9.5% 1400 ± 2% -4.8% 1472 ± 5% stress-ng.inotify.ops_per_sec 11292 ± 8% -2.8% 10974 ± 8% +1.9% 11505 ± 13% -9.4% 10225 ± 6% stress-ng.kill.ops 28.20 ± 4% -35.4% 18.22 -33.5% 18.75 -33.4% 18.77 stress-ng.mmapfork.ops_per_sec 1932318 +1.5% 1961688 ± 2% -22.8% 1492231 ± 2% +4.0% 2010509 ± 3% stress-ng.softlockup.ops 1931679 ± 2% +1.5% 1961143 ± 2% -22.8% 1491939 ± 2% +4.0% 2009585 ± 3% stress-ng.softlockup.ops_per_sec 18607406 ± 6% -12.9% 16210450 ± 21% -12.7% 16238693 ± 14% -8.0% 17120880 ± 13% stress-ng.switch.ops 18604406 ± 6% -12.9% 16208270 ± 21% -12.7% 16237956 ± 14% -8.0% 17115273 ± 13% stress-ng.switch.ops_per_sec 2999012 ± 21% -10.1% 2696954 ± 22% -9.1% 2725653 ± 21% -88.5% 344447 ± 11% stress-ng.tee.ops_per_sec 7882 ± 3% -5.4% 7458 ± 4% -4.0% 7566 ± 4% -2.0% 7724 ± 3% stress-ng.vforkmany.ops 7804 ± 3% -5.2% 7400 ± 4% -3.8% 7504 ± 4% -2.0% 7647 ± 3% stress-ng.vforkmany.ops_per_sec 46745421 ± 3% -8.1% 42938569 ± 3% -7.8% 43078233 ± 3% -5.2% 44312072 ± 4% stress-ng.yield.ops 46734472 ± 3% -8.1% 42926316 ± 3% -7.8% 43067447 ± 3% -5.2% 44290338 ± 4% stress-ng.yield.ops_per_sec
On 4/27/2020 8:46 PM, Vincent Guittot wrote: > On Mon, 27 Apr 2020 at 13:35, Hillf Danton <hdanton@sina.com> wrote: >> >> >> On Mon, 27 Apr 2020 11:03:58 +0200 Vincent Guittot wrote: >>> On Sun, 26 Apr 2020 at 14:42, Hillf Danton wrote: >>>> >>>> On 4/21/2020 8:47 AM, kernel test robot wrote: >>>>> >>>>> Greeting, >>>>> >>>>> FYI, we noticed a 56.4% improvement of stress-ng.fifo.ops_per_sec due to commit: >>>>> >>>>> >>>>> commit: 6c8116c914b65be5e4d6f66d69c8142eb0648c22 ("sched/fair: Fix condition of avg_load calculation") >>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master >>>>> >>>>> in testcase: stress-ng >>>>> on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 128G memory >>>>> with following parameters: >>>>> >>>>> nr_threads: 100% >>>>> disk: 1HDD >>>>> testtime: 1s >>>>> class: scheduler >>>>> cpufreq_governor: performance >>>>> ucode: 0xb000038 >>>>> sc_pid_max: 4194304 >>>>> >>>> >>>> We need to handle group_fully_busy in a different way from >>>> group_overloaded as task push does not help grow load balance >>>> in the former case. >>> >>> Have you tested this patch for the UC above ? Do you have figures ? >>> >> No I am looking for a box of 88 threads. Likely to get access to it in >> as early as three weeks. >> >>>> --- a/kernel/sched/fair.c >>>> +++ b/kernel/sched/fair.c >>>> @@ -8744,30 +8744,20 @@ find_idlest_group(struct sched_domain *s >>>> >>>> switch (local_sgs.group_type) { >>>> case group_overloaded: >>>> - case group_fully_busy: >>>> - /* >>>> - * When comparing groups across NUMA domains, it's possible for >>>> - * the local domain to be very lightly loaded relative to the >>>> - * remote domains but "imbalance" skews the comparison making >>>> - * remote CPUs look much more favourable. When considering >>>> - * cross-domain, add imbalance to the load on the remote node >>>> - * and consider staying local. >>>> - */ >>>> - >>>> - if ((sd->flags & SD_NUMA) && >>>> - ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load)) >>>> + if (100 * local_sgs.avg_load <= sd->imbalance_pct * (idlest_sgs.avg_load + imbalance)) >>>> + return idlest; >>> >>> So you have completely removed the NUMA special case without explaining why. >>> >> That was for the local domain that is lightly loaded, as the comment says, >> it now is overloaded. > > The load value is not linked to the overloaded state of the group as > you can be overloaded but still have a low load especially with cgroup > > That's also why there are 2 type of comparison: > an absolute comparison for low load value > and a proportional comparison for normal/high value > >> >>> And you have also removed the tests for small load. >>> >> It is a heuristic I want to avoid. It can be replaced with the load of the >> task in question as best effort. >> >>> Could you explain the rationale behind all these changes ? >>> >>> Also keep in mind that the current version provide +58% improvement >>> for stress-ng.fifo >>> >> Yes it's great. I'm on the minor one. >> >>>> + if (local_sgs.avg_load > idlest_sgs.avg_load + imbalance) >>>> + return idlest; >>>> + else >>>> return NULL; >>>> >>>> + case group_fully_busy: >>>> /* >>>> - * If the local group is less loaded than the selected >>>> - * idlest group don't try and push any tasks. >>>> + * Pushing task to the idlest group will make the target group >>>> + * overloaded, leaving the local group that is overloaded fully busy, >>>> + * thus we earn nothing except for the exchange of group types. >>> >>> For this case both local and idlest are fully busy and in this case >>> one will become overloaded so you must compare the load to be fair in >>> the spread of load >>> >> It may be sooner than thought that the newly overloaded group is looking to >> push task out, and we'll see a task ping-pong if it happens. >> >> >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -8683,15 +8683,11 @@ find_idlest_group(struct sched_domain *s >> struct sched_group *idlest = NULL, *local = NULL, *group = sd->groups; >> struct sg_lb_stats local_sgs, tmp_sgs; >> struct sg_lb_stats *sgs; >> - unsigned long imbalance; >> struct sg_lb_stats idlest_sgs = { >> .avg_load = UINT_MAX, >> .group_type = group_overloaded, >> }; >> >> - imbalance = scale_load_down(NICE_0_LOAD) * >> - (sd->imbalance_pct-100) / 100; >> - >> do { >> int local_group; >> >> @@ -8743,31 +8739,26 @@ find_idlest_group(struct sched_domain *s >> return idlest; >> >> switch (local_sgs.group_type) { >> - case group_overloaded: >> case group_fully_busy: >> - /* >> - * When comparing groups across NUMA domains, it's possible for >> - * the local domain to be very lightly loaded relative to the >> - * remote domains but "imbalance" skews the comparison making >> - * remote CPUs look much more favourable. When considering >> - * cross-domain, add imbalance to the load on the remote node >> - * and consider staying local. >> - */ >> - >> - if ((sd->flags & SD_NUMA) && >> - ((idlest_sgs.avg_load + imbalance) >= local_sgs.avg_load)) >> - return NULL; >> - >> - /* >> - * If the local group is less loaded than the selected >> - * idlest group don't try and push any tasks. >> - */ >> - if (idlest_sgs.avg_load >= (local_sgs.avg_load + imbalance)) >> - return NULL; >> - >> - if (100 * local_sgs.avg_load <= sd->imbalance_pct * idlest_sgs.avg_load) >> - return NULL; >> - break; >> + return NULL; >> + case group_overloaded: >> + /* No push if balanced */ >> + if (100 * local_sgs.avg_load > sd->imbalance_pct * >> + idlest_sgs.avg_load) { >> + unsigned long avg_load; >> + >> + avg_load = task_h_load(p) + idlest_sgs.group_load; >> + avg_load = (avg_load * SCHED_CAPACITY_SCALE) / >> + idlest_sgs.group_capacity; >> + >> + if (100 * local_sgs.avg_load <= sd->imbalance_pct * >> + avg_load) >> + return idlest; >> + >> + if (local_sgs.avg_load > avg_load) >> + return idlest; >> + } >> + return NULL; >> >> case group_imbalanced: >> case group_asym_packing: >>
-- Zhengjun Xing
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