Hi Kuai, here (attached) the promised simple patch. Best, Florian On Tue, Mar 26, 2024 at 4:51 PM Florian-Ewald Müller <florian-ewald.mueller@xxxxxxxxx> wrote: > > Hello Kuai, > > Thank you for your comments and questions. > > About our tests: > - we used many (>= 100) logical volumes (each 100 GiB big) on top of 3 > x md-raid5s (making up a raid50) on 8 SSDs each. > - further we started a fio instance doing random rd/wr (also of random > sizes) on each of those volumes, > > And, yes indeed, as you suggested, we observed some performance change > already after adding (first) wq_has_sleeper(). > The fio IOPS results improved by around 3-4% - but, in my experience, > every fluctuation <= 3% can also have other reasons (e.g. different > timings, temperature on SSDs, etc.). > > Only afterwards, I've also changed the wait queue construct with the > swait variant (sufficient here), as its wake up path is simpler, > faster and with a smaller stack footprint. > Also used the (now since some years available) IDLE state for the > waiting thread to eliminate the (not anymore necessary) checking and > flushing of signals. > This second round of changes, although theoretically an improvement, > didn't bring any measurable performance increase, though. > This was more or less expected. > > If you think, the simple adding of the wq_has_sleeper() is more > justifiable, please apply only this change. > Later today, I'll also send you a patch containing only this simple change. > > Best regards, > Florian > > On Tue, Mar 26, 2024 at 3:09 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > > > Hi, > > > > 在 2024/03/26 13:22, Jinpu Wang 写道: > > > Hi Song, hi Kuai, > > > > > > ping, Any comments? > > > > > > Thx! > > > > > > On Thu, Mar 7, 2024 at 1:08 PM Jack Wang <jinpu.wang@xxxxxxxxx> wrote: > > >> > > >> From: Florian-Ewald Mueller <florian-ewald.mueller@xxxxxxxxx> > > >> > > >> Replace md_thread's wait_event()/wake_up() related calls with their > > >> simple swait~ variants to improve performance as well as memory and > > >> stack footprint. > > >> > > >> Use the IDLE state for the worker thread put to sleep instead of > > >> misusing the INTERRUPTIBLE state combined with flushing signals > > >> just for not contributing to system's cpu load-average stats. > > >> > > >> Also check for sleeping thread before attempting its wake_up in > > >> md_wakeup_thread() for avoiding unnecessary spinlock contention. > > > > I think it'll be better to split this into a seperate patch. > > And can you check if we just add wq_has_sleeper(), will there be > > performance improvement? > > > > >> > > >> With this patch (backported) on a kernel 6.1, the IOPS improved > > >> by around 4% with raid1 and/or raid5, in high IO load scenarios. > > > > Can you be more specifical about your test? because from what I know, > > IO fast path doesn't involved with daemon thread, and I don't understand > > yet where the 4% improvement is from. > > > > Thanks, > > Kuai > >
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md-6.9-md-thread.patch1
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