Re: [LSF/MM/BPF Topic] synthetic mm testing like page migration

[Luis Chamberlain <mcgrof@kernel.org>]

On Thu, Mar 27, 2025 at 07:46:03AM +1100, Dave Chinner wrote:
> On Wed, Mar 26, 2025 at 11:59:48AM -0700, Luis Chamberlain wrote:
> > I'd like to propose this as a a BoF for MM.
> > 
> > We can find issues if we test them, but some bugs are hard to reproduce,
> > specially some mm bugs. How far are we willing to add knobs to help with
> > synthetic tests which which may not apply to numa for instance? An
> > example is the recent patch I just posted to force testing page
> > migration [0]. We can only run that test if we have a numa system, and a
> > lot of testing today runs on guests without numa. Would we be willing
> > to add a fake numa node to help with synthetic tests like page
> > migration?
> 
> Boot your test VMs with fake-numa=4, and now you have a 4 node
> system being tested even though it's not a real, physical numa
> machine.  I've been doing this for the best part of 15 years now
> with a couple of my larger test VMs explicitly to test NUMA
> interactions.

Suuuuweet! Given your long term use of it, we'll just make it a default
for all kdevops libvirt testing now!

> One of the eventual goals of check-parallel is to have all these
> things environmental variables like memory load, compaction, cpu
> hotplug, etc to be changing in the background whilst the tests
> running so that we can exercise all the filesystem functionality
> under changing MM and environmental conditions without having to
> code that into individual tests....

Indeed, I have high hopes for check-parallel.

  Luis