Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count

From	"Luis R. Rodriguez" <mcgrof@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count
Date	2017-05-25 23:40 +0200
Message-ID	<tL8Ea-5bb-23@gated-at.bofh.it> (permalink)
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On Thu, May 25, 2017 at 12:01 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> On Thu, May 25, 2017 at 11:26 AM, Dmitry Torokhov
> <dmitry.torokhov@gmail.com> wrote:
>> On Thu, May 25, 2017 at 08:06:03PM +0200, Luis R. Rodriguez wrote:
>>> On Thu, May 25, 2017 at 10:38:40AM -0700, Luis R. Rodriguez wrote:
>>> > On Thu, May 25, 2017 at 10:30 AM, Dmitry Torokhov
>>> > > There is
>>> > > no slippery slope for systems to move away, no need to backport
>>> > > anything. We seem to agree that a better solution is possible (throttle
>>> > > number of concurrently running modprobes without killing requesters),
>>> > > and with that solution the band-aid will no longer be needed.
>>> > >
>>> > > So please implement and post the proper fix for the issue.
>>> >
>>> > Alright, will do away with this patch and just go for the jugular of the issue.
>>>
>>> I gave this some more thought, even if we go with the throttling right away in
>>> practice you'll end up with a dmesg notice of a throttle kicking in once you *do*
>>
>> So remove it. The warning was meaningful when we rejected requests, now
>> it is not.
>
> Great.
>
>>> reach this. We are forcing only 50 concurrent threads and making this a static
>>> limit with no good reason than 2.3.38 days evaluation from 16 years ago (2000).
>>> If we throttle we are going to throttle with a 2.3.38 days limit. And you
>>> advocate that ?
>>
>> Yes. Can you give me reason why slamming the system with more than 50
>> modprobes is a good idea in 4.12 days? Does the increased limit
>> decreases boot time? By how much?
>
> If in practice we are not hitting the limit the point is moot, and
> when we do I agree we can re-evaluate. With my stress test driver on a
> test case we can push as hard as bringing out the OOM killer even if
> we throttle, fun.

Alright, I don't see these OOMs anymore *after* I actually nuked that
patch which incremented the kmod limit. The reason we can OOM is
finit_module() can consume gobs of memory, the current value then
seems fair, and work well for my tests provided we do use the proper
throttle. Will respin.

  Luis

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Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 18:30 +0200
  Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-05-25 18:40 +0200
    Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 19:00 +0200
      Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-05-25 19:40 +0200
        Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 19:40 +0200
          Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 20:10 +0200
            Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count Dmitry Torokhov <dmitry.torokhov@gmail.com> - 2017-05-25 20:30 +0200
              Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 21:10 +0200
                Re: [PATCH 1/6] kmod: add dynamic max concurrent thread count "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 23:40 +0200

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