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?
