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

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Message-ID: <eaa75ce0-7064-7919-0e72-6bb4ccc5d0d6@redhat.com>
Date:   Tue, 21 Mar 2023 16:11:27 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Adam Manzanares <a.manzanares@...sung.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 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.

> 
>> 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.

> 
>>> Please collect systemd-analyze given lack of any other tool to evaluate
>>> any deltas. Can't think of anything else to gather other than seeing if
>>> it booted.
>>
>> Issue is that some services (kdump, tuned) seem to take sometimes ages on
>> that system to start for some reason,
> 
> How about disabling that?

It seems to be random services. On my debug kernel with KASAN everything 
is just super slow. I'll try to measure on a !debug kernel.

-- 
Thanks,

David / dhildenb