Re: [PATCH RT 0/6] Linux 3.14.48-rt49-rc1
From: Paul Gortmaker
Date: Sat Aug 08 2015 - 20:07:51 EST
[Re: [PATCH RT 0/6] Linux 3.14.48-rt49-rc1] On 08/08/2015 (Sat 19:23) Steven Rostedt wrote:
> On Sat, 8 Aug 2015 19:10:17 -0400
> Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> wrote:
>
>
> > So we took 20 IRQs in 5s, or 4/s ; not quite the 1/s minimum, but definitely not
> > the HZ/s we'd get w/o NOHZ_FULL. Re-running it got consistently 18-20 IRQ / 5s.
>
> OK, so NO_HZ_FULL still isn't great on -rt, but this shows that it
> keeps disturbances much lower than without it.
Here is several runs on vanilla ("make oldconfig" of the -rt .config)
and all else (bootargs, isolation, rcu offload) the same:
--------------------------------------------------
root@testbox:/home/paul# ./t
LOC: 86341 740 724 708 694 679 663 649 633 619 545 526 512 494 481 463 448 434 420 404 Local timer interrupts
LOC: 91349 742 727 708 694 679 663 649 633 619 545 526 512 496 483 465 450 436 423 406 Local timer interrupts
LOC: 96353 742 727 710 697 709 665 651 635 622 547 528 514 496 483 465 450 436 423 406 Local timer interrupts
root@testbox:/home/paul# ./t
LOC: 106188 744 729 712 699 711 667 653 638 624 549 530 514 498 485 467 452 438 425 408 Local timer interrupts
LOC: 111194 746 729 712 699 711 667 653 638 624 549 530 516 500 487 469 454 440 427 410 Local timer interrupts
LOC: 116199 746 731 714 701 729 669 655 640 626 551 532 516 500 487 469 454 440 427 410 Local timer interrupts
root@testbox:/home/paul# ./t
LOC: 122860 748 733 716 703 731 669 655 640 626 551 532 518 502 489 471 456 442 429 412 Local timer interrupts
LOC: 127866 748 733 716 703 731 671 657 642 628 553 534 520 504 492 473 456 442 429 412 Local timer interrupts
LOC: 132872 750 735 718 706 748 671 657 642 628 553 534 520 504 492 473 458 444 431 415 Local timer interrupts
root@testbox:/home/paul# cat /proc/version
Linux version 3.14.48 (paul@yow-dellw-pg2) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #2 SMP PREEMPT Sat Aug 8 19:52:12 EDT 2015
root@testbox:/home/paul#
--------------------------------------------------
So 30, 18, and 17 per 5s interval. I'd say that is statisitcally close
enough to -rt on this simple test to call -rt on par with vanilla.
Things might show a difference with more complicated tests, more cores
doing real work etc etc. -- this really is just a simple sanity test
though... but at least it is a test that we now can pass!
Paul.
--
>
> Thanks for the report!
>
> -- Steve
>
> >
> > I specifically did NOT unplug and replug cores to "clean" them of tasks; the
> > hotplug code just seems to unstable for that from what I've seen in the past,
> > and by the looks of the irq counts above, there was no need to either.
> >
> > The rootfs was basically a ubu 14.10 server install (no X11/gfx) -- not that
> > it should matter - so long as other tasks weren't running on the nohz cores.
> >
> > Paul.
> > --
> >
> > >
> > > Enjoy,
> > >
> > > -- Steve
> > >
>
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