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

Breno Leitao
2025-04-16T14:14:09Z

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]

Thanks for working on it,
--breno