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

Luis R. Rodriguez
2017-05-25T19:02:04Z

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.

Luis