Re: [PATCH 0/4] Fix scalability problem in workqueue watchdog touch caused by stop_machine

[Srikar Dronamraju <srikar@linux.ibm.com>]

* Nicholas Piggin <npiggin@gmail.com> [2024-06-26 10:57:36]:

> On Wed Jun 26, 2024 at 12:53 AM AEST, Paul E. McKenney wrote:
> > On Tue, Jun 25, 2024 at 09:42:43PM +1000, Nicholas Piggin wrote:
> > > Here are a few patches to fix a lockup caused by very slow progress due
> > > to a scalability problem in workqueue watchdog touch being hammered by
> > > thousands of CPUs in multi_cpu_stop. Patch 2 is the fix.
> > > 
> > > I did notice when making a microbenchmark reproducer that the RCU call
> > > was actually also causing slowdowns. Not nearly so bad as the workqueue
> > > touch, but workqueue queueing of dummy jobs slowed down by a factor of
> > > several times when lots of other CPUs were making
> > > rcu_momentary_dyntick_idle() calls. So I did the stop_machine patches to
> > > reduce that. So those patches 3,4 are independent of the first two and
> > > can go in any order.
> >
> > For the series:
> >
> > Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> 
> Oh, it did get a comment :) Thanks Paul. Not sure who owns the
> multi_cpu_stop loop, Tejun and Peter I guess but that was 10+
> years ago :P
> 
> I might ask Andrew if he would take patches 3-4, if there are
> no objections.
> 

patches 3 and 4 are still not part of any tree.
Can we please include them or are there any reservations on them.

The patches still seem to apply on top of Linus tree except one line where
rcu_momentary_dyntick_idle() has been renamed to rcu_momentary_eqs()

Commit 32a9f26e5e26 ("rcu: Rename rcu_momentary_dyntick_idle() into
rcu_momentary_eqs()") 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/patch/?id=32a9f26e5e26

-- 
Thanks and Regards
Srikar Dronamraju