Re: [PATCH v5 0/8] Generic IRQ entry/exit support for powerpc

[Jirka Hladky]

Hi Mukesh,

I built 7.2-rc4 from source with your proposed rcu_ct_kernel_exit_qs()
patch and re-ran the same sweep - it shows minor improvements vs. stock
7.2-rc4

Full results, median bogo-ops/sec over 15 runs each:

  Mode          7.1        7.2-rc4     7.2-rc4+patch
  Enforcing     68,275     70,154      71,585
  Permissive    68,082     67,166      68,705
  Disabled      99,654     100,510     101,016

The patch vs. stock 7.2-rc4 differences (+4.8%/+0.9%/+1.3%) are hard
to distinquish
from run-to-run noise we've been seeing on this hardware, but they are
consistent.

I think it's a useful efficiency improvement on its own merits, as it
does avoid the unconditional rcu_preempt_deferred_qs() call on the common
fast path. Even with only small performance gains, the change looks correct
and low-risk to me, and I'd like to see it land in mainline. Let me
know if there's
anything else you'd like me to test before you post it, or if it's
already queued up
separately from this thread.

Thank you!
Jirka


On Fri, Sep 11, 2026 at 12:54 PM Jirka Hladky <jhladky@xxxxxxxxxx> wrote:
>
> Hi Mukesh,
>
> I built 7.2-rc4 from source with your proposed rcu_ct_kernel_exit_qs()
> patch and re-ran the same sweep - it shows minor improvements vs. stock
> 7.2-rc4
>
> Full results, median bogo-ops/sec over 15 runs each:
>
>   Mode          7.1        7.2-rc4     7.2-rc4+patch
>   Enforcing     68,275     70,154      71,585
>   Permissive    68,082     67,166      68,705
>   Disabled      99,654     100,510     101,016
>
> The patch vs. stock 7.2-rc4 differences (+4.8%/+0.9%/+1.3%) are hard to distinquish
> from run-to-run noise we've been seeing on this hardware, but they are consistent.
>
> I think it's a useful efficiency improvement on its own merits, as it
> does avoid the unconditional rcu_preempt_deferred_qs() call on the common
> fast path. Even with only small performance gains, the change looks correct
> and low-risk to me, and I'd like to see it land in mainline. Let me know if there's
> anything else you'd like me to test before you post it, or if it's already queued up
> separately from this thread.
>
> Thank you!
> Jirka
>
> On Fri, Sep 11, 2026 at 7:12 AM Mukesh Kumar Chaurasiya <mkchauras@xxxxxxxxx> wrote:
>>
>> On Thu, Sep 10, 2026 at 09:58:59PM +0200, Jirka Hladky wrote:
>> > Oh, I forgot to add the actual results from the LPAR:
>> >
>> > Model name:                  POWER10 (architected), altivec supported
>> > Model:                     2.0 (pvr 0080 0200)
>> > Type                                         : Dedicated
>> > Mode                                         : Capped
>> > Entitled Capacity                            : 1.00
>> > Memory Mode                                  : Dedicated
>> >
>> > Results (median bogo-ops/sec, N=15 per cell):
>> >   Mode          7.1        7.2-rc4      Delta
>> >   Enforcing     68,275     70,154       +2.7%
>> >   Permissive    68,082     67,166       -1.3%
>> >   Disabled      99,654     100,510      +0.9%
>> >
>> [...]
>> Hey Jirka,
>>
>> Thanks for confirming. Also with the diff I shared, did you see any
>> difference in the performance.
>>
>> Regards,
>> Mukesh
>>
>
>
> --
> -Jirka



-- 
-Jirka