Messages in this thread | | | Date | Wed, 4 Oct 2023 19:48:01 +0200 | From | Peter Zijlstra <> | Subject | Re: EEVDF and NUMA balancing |
| |
On Wed, Oct 04, 2023 at 06:24:39PM +0200, Julia Lawall wrote: > > > On Wed, 4 Oct 2023, Peter Zijlstra wrote: > > > On Wed, Oct 04, 2023 at 02:01:26PM +0200, Julia Lawall wrote: > > > > > > > > > On Tue, 3 Oct 2023, Peter Zijlstra wrote: > > > > > > > On Tue, Oct 03, 2023 at 10:25:08PM +0200, Julia Lawall wrote: > > > > > Is it expected that the commit e8f331bcc270 should have an impact on the > > > > > frequency of NUMA balancing? > > > > > > > > Definitely not expected. The only effect of that commit was supposed to > > > > be the runqueue order of tasks. I'll go stare at it in the morning -- > > > > definitely too late for critical thinking atm. > > > > > > Maybe it's just randomly making a bad situation worse rather than directly > > > introduing a problem. There is a high standard deviatind in the > > > performance. Here are some results with hyperfine. The general trends > > > are reproducible. > > > > OK,. I'm still busy trying to bring a 4 socket machine up-to-date... > > gawd I hate the boot times on those machines :/ > > > > But yeah, I was thinking similar things, I really can't spot an obvious > > fail in that commit. > > > > I'll go have a poke once the darn machine is willing to submit :-) > > I tried a two-socket machine, but in 50 runs the problem doesn't show up.
I've had to re-install the 4 socket thing -- lost the day to this trainwreck :/ Because obvoiusly the BMC needs Java and that all don't work anymore -- so I had to go sit next to the jet-engine thing with a keyboard and monitor.
I'll go build the benchmark thing tomorrow, if I can figure out how that works, this NAS stuff looked 'special'. Nothing simple like ./configure; make -j$lots :/
> The commit e8f331bcc270 starts with > > - if (sched_feat(PLACE_LAG) && cfs_rq->nr_running > 1) { > + if (sched_feat(PLACE_LAG) && cfs_rq->nr_running) { > > This seemed like a big change - cfs_rq->nr_running > 1 should be rarely > true in ua, while cfs_rq->nr_running should always be true. Adding back > the > 1 and simply replacing the test by 0 both had no effect, though.
Yeah, this is because I flip the order of place_entity() and nr_running++ around later in the patch. Previously it would increment before place, now it does place before increment.
| |