Messages in this thread | | | Date | Fri, 18 Feb 2022 12:00:41 +0100 | Subject | Re: [REGRESSION] 5-10% increase in IO latencies with nohz balance patch | From | Thorsten Leemhuis <> |
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Hi, this is your Linux kernel regression tracker speaking. Top-posting for once, to make this easy accessible to everyone.
FWIW, this is a gentle reminder that I'm still tracking this regression. Afaics nothing happened in the last few weeks.
If the discussion continued somewhere else, please let me know; you can do this directly or simply tell my regression tracking bot yourself by sending a reply to this mail with a paragraph containing a regzbot command like "#regzbot monitor https://lore.kernel.org/r/some_msgi@example.com/"
If you think there are valid reasons to drop this regressions from the tracking, let me know; you can do this directly or simply tell my regression tracking bot yourself by sending a reply to this mail with a paragraph containing a regzbot command like "#regzbot invalid: Some explanation" (without the quotes).
Anyway: I'm putting it on back burner now to reduce the noise, as this afaics is less important than other regressions:
#regzbot backburner: Culprit is hard to track down #regzbot poke
You likely get two more mails like this after the next two merge windows, then I'll drop it if I don't here anything back.
Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
P.S.: As the Linux kernel's regression tracker I'm getting a lot of reports on my table. I can only look briefly into most of them and lack knowledge about most of the areas they concern. I thus unfortunately will sometimes get things wrong or miss something important. I hope that's not the case here; if you think it is, don't hesitate to tell me in a public reply, it's in everyone's interest to set the public record straight.
On 13.01.22 17:57, Roman Gushchin wrote: > On Thu, Jan 13, 2022 at 04:41:57PM +0000, Valentin Schneider wrote: >> On 03/01/22 11:16, Josef Bacik wrote: >>> On Wed, Dec 22, 2021 at 04:07:35PM +0000, Valentin Schneider wrote: >>>> >>>> Hi, >>>> >>>> On 22/12/21 13:42, Thorsten Leemhuis wrote: >>>>> What's the status here? Just wondering, because there hasn't been any >>>>> activity in this thread since 11 days and the festive season is upon us. >>>>> >>>>> Was the discussion moved elsewhere? Or is this still a mystery? And if >>>>> it is: how bad is it, does it need to be fixed before Linus releases 5.16? >>>>> >>>> >>>> I got to the end of bisect #3 yesterday, the incriminated commit doesn't >>>> seem to make much sense but I've just re-tested it and there is a clear >>>> regression between that commit and its parent (unlike bisect #1 and #2): >>>> >>>> 2127d22509aec3a83dffb2a3c736df7ba747a7ce mm, slub: fix two bugs in slab_debug_trace_open() >>>> write_clat_ns_p99 195395.92 199638.20 4797.01 2.17% >>>> write_iops 17305.79 17188.24 250.66 -0.68% >>>> >>>> write_clat_ns_p99 195543.84 199996.70 5122.88 2.28% >>>> write_iops 17300.61 17241.86 251.56 -0.34% >>>> >>>> write_clat_ns_p99 195543.84 200724.48 5122.88 2.65% >>>> write_iops 17300.61 17246.63 251.56 -0.31% >>>> >>>> write_clat_ns_p99 195543.84 200445.41 5122.88 2.51% >>>> write_iops 17300.61 17215.47 251.56 -0.49% >>>> >>>> 6d2aec9e123bb9c49cb5c7fc654f25f81e688e8c mm/mempolicy: do not allow illegal MPOL_F_NUMA_BALANCING | MPOL_LOCAL in mbind() >>>> write_clat_ns_p99 195395.92 197942.30 4797.01 1.30% >>>> write_iops 17305.79 17246.56 250.66 -0.34% >>>> >>>> write_clat_ns_p99 195543.84 196183.92 5122.88 0.33% >>>> write_iops 17300.61 17310.33 251.56 0.06% >>>> >>>> write_clat_ns_p99 195543.84 196990.71 5122.88 0.74% >>>> write_iops 17300.61 17346.32 251.56 0.26% >>>> >>>> write_clat_ns_p99 195543.84 196362.24 5122.88 0.42% >>>> write_iops 17300.61 17315.71 251.56 0.09% >>>> >>>> It's pure debug stuff and AFAICT is a correct fix... >>>> @Josef, could you test that on your side? >>> >>> Sorry, holidays and all that. I see 0 difference between the two commits, and >>> no regression from baseline. It'll take me a few days to recover from the >>> holidays, but I'll put some more effort into actively debugging wtf is going on >>> here on my side since we're all having trouble pinning down what's going >>> on. >> >> Humph, that's unfortunate... I just came back from my holidays, so I'll be >> untangling my inbox for the next few days. Do keep us posted! > > I'm trying to bisect it independently and make sense of it too, thanks to Josef > for providing me a test setup. From the very first data I've got yesterday, > the only thing I can say the data is very noisy and I'm not totally convinced > that the regression is coming from the patch which was blamed initially. > > I hope to make more progress today/tomorrow, will keep you updated. > > Thanks! >
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