Messages in this thread Patch in this message | | | Date | Mon, 27 Mar 2023 11:09:51 +0200 | From | Peter Zijlstra <> | Subject | Re: rq lock contention due to commit af7f588d8f73 |
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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.
Can you frob init/Kconfig and make SCHED_MM_CID user configurable and disable it to confirm?
(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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