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

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Message-ID: <f18ec4d3-be63-7e86-1951-f3d460acd7a7@redhat.com>
Date:   Wed, 15 Mar 2023 17:41:53 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
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 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@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.

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