Re: [RFC PATCH 0/8] Introduce simple hazard pointers for lockdep

Uladzislau Rezki
2025-04-16T15:04:38Z

On Wed, Apr 16, 2025 at 07:14:04AM -0700, Breno Leitao wrote:
> Hi Boqun,
>
> On Sun, Apr 13, 2025 at 11:00:47PM -0700, Boqun Feng wrote:
>
> > Overall it looks promising to me, but I would like to see how it
> > performs in the environment of Breno. Also as Paul always reminds me:
> > buggy code usually run faster, so please take a look in case I'm missing
> > something ;-) Thanks!
>
> Thanks for the patchset. I've confirmed that the wins are large on my
> environment, but, at the same magnitute of synchronize_rcu_expedited().
>
> Here are the numbers I got:
>
> 6.15-rc1 (upstream)
> # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq
> real 0m3.986s
> user 0m0.001s
> sys 0m0.093s
>
> Your patchset on top of 6.15-rc1
> # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq
> real 0m0.072s
> user 0m0.001s
> sys 0m0.070s
>
>
> My original proposal of using synchronize_rcu_expedited()[1]
> # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq
> real 0m0.074s
> user 0m0.001s
> sys 0m0.061s
>
> Link: https://lore.kernel.org/all/20250321-lockdep-v1-1-78b732d195fb@debian.org/ [1]
>
Could you please also do the test of fist scenario with a regular
synchronize_rcu() but switch to its faster variant:

echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp

and run the test. If you have a time.

Thank you!

--
Vlad Rezki