> -----Original Message----- > From: Dietmar Eggemann [mailto:dietmar.eggemann@xxxxxxx] > Sent: Friday, May 14, 2021 12:32 AM > To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>; Vincent Guittot > <vincent.guittot@xxxxxxxxxx> > Cc: tim.c.chen@xxxxxxxxxxxxxxx; catalin.marinas@xxxxxxx; will@xxxxxxxxxx; > rjw@xxxxxxxxxxxxx; bp@xxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; > lenb@xxxxxxxxxx; peterz@xxxxxxxxxxxxx; rostedt@xxxxxxxxxxx; > bsegall@xxxxxxxxxx; mgorman@xxxxxxx; msys.mizuma@xxxxxxxxx; > valentin.schneider@xxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; Jonathan Cameron > <jonathan.cameron@xxxxxxxxxx>; juri.lelli@xxxxxxxxxx; mark.rutland@xxxxxxx; > sudeep.holla@xxxxxxx; aubrey.li@xxxxxxxxxxxxxxx; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > linux-acpi@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx; xuwei (O) <xuwei5@xxxxxxxxxx>; > Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; guodong.xu@xxxxxxxxxx; yangyicong > <yangyicong@xxxxxxxxxx>; Liguozhu (Kenneth) <liguozhu@xxxxxxxxxxxxx>; > linuxarm@xxxxxxxxxxxxx; hpa@xxxxxxxxx > Subject: Re: [RFC PATCH v6 3/4] scheduler: scan idle cpu in cluster for tasks > within one LLC > > On 07/05/2021 15:07, Song Bao Hua (Barry Song) wrote: > > > > > >> -----Original Message----- > >> From: Dietmar Eggemann [mailto:dietmar.eggemann@xxxxxxx] > > [...] > > >> On 03/05/2021 13:35, Song Bao Hua (Barry Song) wrote: > >> > >> [...] > >> > >>>> From: Song Bao Hua (Barry Song) > >> > >> [...] > >> > >>>>> From: Dietmar Eggemann [mailto:dietmar.eggemann@xxxxxxx] > >> > >> [...] > >> > >>>>> On 29/04/2021 00:41, Song Bao Hua (Barry Song) wrote: > >>>>>> > >>>>>> > >>>>>>> -----Original Message----- > >>>>>>> From: Dietmar Eggemann [mailto:dietmar.eggemann@xxxxxxx] > >>>>> > >>>>> [...] > >>>>> > >>>>>>>>>> From: Dietmar Eggemann [mailto:dietmar.eggemann@xxxxxxx] > >>>>>>> > >>>>>>> [...] > >>>>>>> > >>>>>>>>>> On 20/04/2021 02:18, Barry Song wrote: > >> > >> [...] > >> > >>> > >>> On the other hand, according to "sched: Implement smarter wake-affine logic" > >>> > >> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/ > >> ?id=62470419 > >>> > >>> Proper factor in wake_wide is mainly beneficial of 1:n tasks like > >> postgresql/pgbench. > >>> So using the smaller cluster size as factor might help make wake_affine > false > >> so > >>> improve pgbench. > >>> > >>> From the commit log, while clients = 2*cpus, the commit made the biggest > >>> improvement. In my case, It should be clients=48 for a machine whose LLC > >>> size is 24. > >>> > >>> In Linux, I created a 240MB database and ran "pgbench -c 48 -S -T 20 pgbench" > >>> under two different scenarios: > >>> 1. page cache always hit, so no real I/O for database read > >>> 2. echo 3 > /proc/sys/vm/drop_caches > >>> > >>> For case 1, using cluster_size and using llc_size will result in similar > >>> tps= ~108000, all of 24 cpus have 100% cpu utilization. > >>> > >>> For case 2, using llc_size still shows better performance. > >>> > >>> tps for each test round(cluster size as factor in wake_wide): > >>> 1398.450887 1275.020401 1632.542437 1412.241627 1611.095692 1381.354294 > >> 1539.877146 > >>> avg tps = 1464 > >>> > >>> tps for each test round(llc size as factor in wake_wide): > >>> 1718.402983 1443.169823 1502.353823 1607.415861 1597.396924 1745.651814 > >> 1876.802168 > >>> avg tps = 1641 (+12%) > >>> > >>> so it seems using cluster_size as factor in "slave >= factor && master >= > >> slave * > >>> factor" isn't a good choice for my machine at least. > >> > >> So SD size = 4 (instead of 24) seems to be too small for `-c 48`. > >> > >> Just curious, have you seen the benefit of using wake wide on SD size = > >> 24 (LLC) compared to not using it at all? > > > > At least in my benchmark made today, I have not seen any benefit to use > > llc_size. Always returning 0 in wake_wide() seems to be much better. > > > > postgres@ubuntu:$pgbench -i pgbench > > postgres@pgbench:$ pgbench -T 120 -c 48 pgbench > > > > using llc_size, it got to 123tps > > always returning 0 in wake_wide(), it got to 158tps > > > > actually, I really couldn't reproduce the performance improvement > > the commit "sched: Implement smarter wake-affine logic" mentioned. > > on the other hand, the commit log didn't present the pgbench command > > parameter used. I guess the benchmark result will highly depend on > > the command parameter and disk I/O speed. > > I see. And it was a way smaller machine (12 CPUs) back then. > > You could run pgbench via mmtests https://github.com/gormanm/mmtests. > > I.e the `timed-ro-medium` test. > > mmtests# ./run-mmtests.sh --config > ./configs/config-db-pgbench-timed-ro-medium test_tag > > /shellpacks/shellpack-bench-pgbench contains all the individual test > steps. Something you could use as a template for your pgbench standalone > tests as well. > > I ran this test on an Intel Xeon E5-2690 v2 with 40 CPUs and 64GB of > memory on v5.12 vanilla and w/o wakewide. > The test uses `scale_factor = 2570` on this machine. I guess this > relates to ~41GB? At least this was the size of the: Thanks. Dietmar, sorry for slow response. Sick leave for the whole last week. I feel it makes much more sense to use mmtests which is setting scale_factor according to total memory size, thus, considering the impact of page cache. And it is also doing database warming-up for 30minutes. I will get more data and compare three cases: 1. use cluster as wake_wide factor 2. use llc as wake_wide factor 3. always return 0 in wake_wide. and post the result afterwards. > > #mmtests/work/testdisk/data/pgdata directory when the test started. > > > mmtests/work/log# ../../compare-kernels.sh --baseline base --compare > wo_wakewide | grep ^Hmean > > > #clients v5.12 vanilla v5.12 w/o wakewide > > Hmean 1 10903.88 ( 0.00%) 10792.59 * -1.02%* > Hmean 6 28480.60 ( 0.00%) 27954.97 * -1.85%* > Hmean 12 49197.55 ( 0.00%) 47758.16 * -2.93%* > Hmean 22 72902.37 ( 0.00%) 71314.01 * -2.18%* > Hmean 30 75468.16 ( 0.00%) 75929.17 * 0.61%* > Hmean 48 60155.58 ( 0.00%) 60471.91 * 0.53%* > Hmean 80 62202.38 ( 0.00%) 60814.76 * -2.23%* > > > So there are some improvements w/ wakewide but nothing of the scale > showed in the original wakewide patch. > > I'm not an expert on how to set up these pgbench tests though. So maybe > other pgbench related mmtests configs or some more fine-grained tuning > can produce bigger diffs? Thanks Barry
