Messages in this thread | | | Date | Mon, 27 Mar 2023 18:14:01 +0800 | From | Aaron Lu <> | Subject | Re: rq lock contention due to commit af7f588d8f73 |
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On Mon, Mar 27, 2023 at 11:09:51AM +0200, Peter Zijlstra wrote: > On Mon, Mar 27, 2023 at 04:05:02PM +0800, Aaron Lu wrote: > > Hi Mathieu, > > > > I was doing some optimization work[1] for kernel scheduler using a > > database workload: sysbench+postgres and before I submit my work, I > > rebased my patch on top of latest v6.3-rc kernels to see if everything > > still works expected and then I found rq's lock became very heavily > > contended as compared to v6.2 based kernels. > > > > Using the above mentioned workload, before commit af7f588d8f73("sched: > > Introduce per-memory-map concurrency ID"), the profile looked like: > > > > 7.30% 0.71% [kernel.vmlinux] [k] __schedule > > 0.03% 0.03% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath > > > > After that commit: > > > > 49.01% 0.87% [kernel.vmlinux] [k] __schedule > > 43.20% 43.18% [kernel.vmlinux] [k] native_queued_spin_lock_slowpath > > Unlike what the subject says, if it is due to that commit, then it's not > rq lock but that new cid_lock thing.
Ah my mistake. I didn't take a closer look at the commit and seeing __schedule path has lock contention made me think it is rq->lock.
> > Can you frob init/Kconfig and make SCHED_MM_CID user configurable and > disable it to confirm?
Sure thing, compiling now and will let you know the result once done.
> > (also, mathieu, when you do the below, you'll see it is in a weird spot) > > diff --git a/init/Kconfig b/init/Kconfig > index 1fb5f313d18f..f2661f73f3dd 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1042,7 +1042,8 @@ config RT_GROUP_SCHED > endif #CGROUP_SCHED > > config SCHED_MM_CID > - def_bool y > + bool "RSEQ Concurrency ID" > + default y > depends on SMP && RSEQ > > config UCLAMP_TASK_GROUP
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