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

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Date:   Tue, 21 Mar 2023 18:01:40 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Adam Manzanares <a.manzanares@...sung.com>,
        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 21.03.23 17:52, Luis Chamberlain wrote:
> On Tue, Mar 21, 2023 at 04:11:27PM +0100, David Hildenbrand wrote:
>> On 20.03.23 22:23, Luis Chamberlain wrote:
>>> On Mon, Mar 20, 2023 at 10:15:23PM +0100, David Hildenbrand wrote:
>>>> On 20.03.23 22:09, Luis Chamberlain wrote:
>>>>> On Mon, Mar 20, 2023 at 08:40:07PM +0100, David Hildenbrand wrote:
>>>>>> On 20.03.23 10:38, David Hildenbrand wrote:
>>>>>>> On 18.03.23 01:11, Luis Chamberlain wrote:
>>>>>>>> On Thu, Mar 16, 2023 at 04:56:56PM -0700, Luis Chamberlain wrote:
>>>>>>>>> On Thu, Mar 16, 2023 at 04:55:31PM -0700, Luis Chamberlain wrote:
>>>>>>>>>> On Wed, Mar 15, 2023 at 05:41:53PM +0100, David Hildenbrand wrote:
>>>>>>>>>>> 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.
>>>>>>>>>>
>>>>>>>>>> OK give this a spin:
>>>>>>>>>>
>>>>>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230316-module-alloc-opts
>>>>>>>>
>>>>>>>> Today I am up to here:
>>>>>>>>
>>>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230317-module-alloc-opts
>>>>>>>>
>>>>>>>> The last patch really would have no justification yet at all unless it
>>>>>>>> does help your case.
>>>>>>>
>>>>>>> Still waiting on the system (the replacement system I was able to grab
>>>>>>> broke ...).
>>>>>>>
>>>>>>> I'll let you know once I succeeded in reproducing + testing your fixes.
>>>>>>
>>>>>> Okay, I have a system where I can reproduce.
>>>>>>
>>>>>> Should I give
>>>>>>
>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git/log/?h=20230319-module-alloc-opts
>>>>>>
>>>>>> from yesterday a churn?
>>>>>
>>>>> Yes please give that a run.
>>>>
>>>> Reproduced with v6.3.0-rc1 (on 1st try)
>>>
>>> By reproduced, you mean it fails to boot?
>>
>> It boots but we get vmap allocation warnings, because the ~440 CPUs manage
>> to completely exhaust the module vmap area due to KASAN.
> 
> Thanks, can you post a trace?

See

https://lkml.kernel.org/r/20221013180518.217405-1-david@redhat.com

where I also describe the issue in more detail.

> 
>>>> Not able to reproduce with 20230319-module-alloc-opts so far (2 tries).
>>>
>>> Oh wow, so to clarify, it boots OK?
>>
>> It boots and I don't get the vmap allocation warnings.
> 
> Wonderful!

I'm still compiling/testing the debug kernels 
(20230319-module-alloc-opts-adjust +  single revert of the rcu patch). I 
should have some systemd-analyze results for !debug kernels later.

-- 
Thanks,

David / dhildenb