On Sun 10-01-21 10:23:47, Paolo Valente wrote: > > > > Il giorno 2 set 2020, alle ore 17:17, Jan Kara <jack@xxxxxxx> ha scritto: > > > > On Wed 26-08-20 15:54:19, Jan Kara wrote: > >> On Mon 27-07-20 09:35:15, Jan Kara wrote: > >>> On Wed 22-07-20 11:13:28, Paolo Valente wrote: > >>>>> a) I don't think adding these samples to statistics helps in any way (you > >>>>> cannot improve the prediction power of the statistics by including in it > >>>>> some samples that are not directly related to the thing you try to > >>>>> predict). And think time is used to predict the answer to the question: If > >>>>> bfq queue becomes idle, how long will it take for new request to arrive? So > >>>>> second and further requests are simply irrelevant. > >>>>> > >>>> > >>>> Yes, you are super right in theory. > >>>> > >>>> Unfortunately this may not mean that your patch will do only good, for > >>>> the concerns in my previous email. > >>>> > >>>> So, here is a proposal to move forward: > >>>> 1) I test your patch on my typical set of > >>>> latency/guaranteed-bandwidth/total-throughput benchmarks > >>>> 2) You test your patch on a significant set of benchmarks in mmtests > >>>> > >>>> What do you think? > >>> > >>> Sure, I will queue runs for the patches with mmtests :). > >> > >> Sorry it took so long but I've hit a couple of technical snags when running > >> these tests (plus I was on vacation). So I've run the tests on 4 machines. > >> 2 with rotational disks with NCQ, 2 with SATA SSD. Results are mostly > >> neutral, details are below. > >> > >> For dbench, it seems to be generally neutral but the patches do fix > >> occasional weird outlier which are IMO caused exactly by bugs in the > >> heuristics I'm fixing. Things like (see the outlier for 4 clients > >> with vanilla kernel): > >> > >> vanilla bfq-waker-fixes > >> Amean 1 32.57 ( 0.00%) 32.10 ( 1.46%) > >> Amean 2 34.73 ( 0.00%) 34.68 ( 0.15%) > >> Amean 4 199.74 ( 0.00%) 45.76 ( 77.09%) > >> Amean 8 65.41 ( 0.00%) 65.47 ( -0.10%) > >> Amean 16 95.46 ( 0.00%) 96.61 ( -1.21%) > >> Amean 32 148.07 ( 0.00%) 147.66 ( 0.27%) > >> Amean 64 291.17 ( 0.00%) 289.44 ( 0.59%) > >> > >> For pgbench and bonnie, patches are neutral for all the machines. > >> > >> For reaim disk workload, patches are mostly neutral, just on one machine > >> with SSD they seem to improve XFS results and worsen ext4 results. But > >> results look rather noisy on that machine so it may be just a noise... > >> > >> For parallel dd(1) processes reading from multiple files, results are also > >> neutral all machines. > >> > >> For parallel dd(1) processes reading from a common file, results are also > >> neutral except for one machine with SSD on XFS (ext4 was fine) where there > >> seems to be consistent regression for 4 and more processes: > >> > >> vanilla bfq-waker-fixes > >> Amean 1 393.30 ( 0.00%) 391.02 ( 0.58%) > >> Amean 4 443.88 ( 0.00%) 517.16 ( -16.51%) > >> Amean 7 599.60 ( 0.00%) 748.68 ( -24.86%) > >> Amean 12 1134.26 ( 0.00%) 1255.62 ( -10.70%) > >> Amean 21 1940.50 ( 0.00%) 2206.29 ( -13.70%) > >> Amean 30 2381.08 ( 0.00%) 2735.69 ( -14.89%) > >> Amean 48 2754.36 ( 0.00%) 3258.93 ( -18.32%) > >> > >> I'll try to reproduce this regression and check what's happening... > >> > >> So what do you think, are you fine with merging my patches now? > > > > Paolo, any results from running your tests for these patches? I'd like to > > get these mostly obvious things merged so that we can move on... > > > > Hi, > sorry again for my delay. Tested this too, at last. No regression. So gladly > > Acked-by: Paolo Valente <paolo.valente@xxxxxxxxxx> > > And thank you very much for your contributions and patience, Thanks. I'll add you ack and send all the patches to Jens. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
