Re: [RFC 00/12] module: avoid userspace pressure on unwanted allocations

[David Hildenbrand]

On 15.03.23 17:10, Luis Chamberlain wrote:
> On Wed, Mar 15, 2023 at 01:24:41PM +0100, David Hildenbrand wrote:
> > On 11.03.23 06:17, Luis Chamberlain wrote:
> > > A long time ago we had some issues with userspace doing stupid stuff.
> > > Well, it turns out even the kernel and do stupid stuff too, as we're
> > > learning with the ACPI modules aliaes and that hammering tons of loads.
> > >
> > > So add a bit of code which gets us a bit more in the defensive about
> > > these situations.
> > >
> > > To experiment, this also adds in-kernel alias support to see if this helps
> > > with some larger systems.
> > >
> > > This is all based on some old code which tried to add defensive
> > > mechanisms the last of which was here and I had dropped the ball:
> > >
> > > https://lore.kernel.org/all/20171208001540.23696-1-mcgrof@xxxxxxxxxx/
> > >
> > > I've only compile tested this for now. Will need to stress to test
> > > with kmod tests 0008 and 0009 to see if there's any differences.
> > > I'll have to re-test and re-gnuplot stuff there. But early feedback
> > > is appreciated, hence the RFC.
> > >
> > > David Hildenbrand had reported a while ago issues with userspace
> > > doing insane things with allocations bringing a system down to
> > > its knees. This is part of the motivation for this series.
> >
> >
> > I'll try to grab a system where I can reproduce the issue and give your
> > patches a churn.
>
> Great, then please wait for v2 RFC as the first patch was missing an
> obvious mutex grab / release, I already have some memory pressure data
> that shows gains. Hope to post soon.

I expect to have a machine (with a crazy number of CPUs/devices) 
available in a couple of days (1-2), so no need to rush.

The original machine I was able to reproduce with is blocked for a 
little bit longer; so I hope the alternative I looked up will similarly 
trigger the issue easily.

--
Thanks,

David / dhildenb