On Wed 12-06-19 12:36:53, Srivatsa S. Bhat wrote: > > [ Adding Greg to CC ] > > On 6/12/19 6:04 AM, Jan Kara wrote: > > On Tue 11-06-19 15:34:48, Srivatsa S. Bhat wrote: > >> On 6/2/19 12:04 AM, Srivatsa S. Bhat wrote: > >>> On 5/30/19 3:45 AM, Paolo Valente wrote: > >>>> > >> [...] > >>>> At any rate, since you pointed out that you are interested in > >>>> out-of-the-box performance, let me complete the context: in case > >>>> low_latency is left set, one gets, in return for this 12% loss, > >>>> a) at least 1000% higher responsiveness, e.g., 1000% lower start-up > >>>> times of applications under load [1]; > >>>> b) 500-1000% higher throughput in multi-client server workloads, as I > >>>> already pointed out [2]. > >>>> > >>> > >>> I'm very happy that you could solve the problem without having to > >>> compromise on any of the performance characteristics/features of BFQ! > >>> > >>> > >>>> I'm going to prepare complete patches. In addition, if ok for you, > >>>> I'll report these results on the bug you created. Then I guess we can > >>>> close it. > >>>> > >>> > >>> Sounds great! > >>> > >> > >> Hi Paolo, > >> > >> Hope you are doing great! > >> > >> I was wondering if you got a chance to post these patches to LKML for > >> review and inclusion... (No hurry, of course!) > >> > >> Also, since your fixes address the performance issues in BFQ, do you > >> have any thoughts on whether they can be adapted to CFQ as well, to > >> benefit the older stable kernels that still support CFQ? > > > > Since CFQ doesn't exist in current upstream kernel anymore, I seriously > > doubt you'll be able to get any performance improvements for it in the > > stable kernels... > > > > I suspected as much, but that seems unfortunate though. The latest LTS > kernel is based on 4.19, which still supports CFQ. It would have been > great to have a process to address significant issues on older > kernels too. Well, you could still tune the performance difference by changing slice_idle and group_idle tunables for CFQ (in /sys/block/<device>/queue/iosched/). Changing these to lower values will reduce the throughput loss when switching between cgroups at the cost of lower accuracy of enforcing configured IO proportions among cgroups. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
