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

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Message-ID: <ZBHuBgUQFbsd6l+J@bombadil.infradead.org>
Date:   Wed, 15 Mar 2023 09:10:46 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
        pmladek@...e.com, petr.pavlu@...e.com, prarit@...hat.com,
        christophe.leroy@...roup.eu, song@...nel.org,
        torvalds@...ux-foundation.org
Subject: Re: [RFC 00/12] module: avoid userspace pressure on unwanted
 allocations

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@kernel.org/
> > 
> > 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.

  Luis