Occasional delayed output of events

[Paul Moore]

On January 17, 2021 4:12:44 PM Steve Grubb <sgrubb at redhat.com> wrote:

> On Sunday, January 17, 2021 9:07:08 AM EST Paul Moore wrote:
>> On Fri, Jan 15, 2021 at 9:43 PM Burn Alting <burn.alting at iinet.net.au>
> wrote:
>>> On Fri, 2021-01-15 at 19:35 -0500, Richard Guy Briggs wrote:
>>>> Or we go back to userspace code looking for the EOE record?  This
>>>> doesn't help if they arrive out of order.  Do we number the records in
>>>> the kernel?  N of M...
>>>
>>> I like the N of M concept but there would be a LOT of change - especially
>>> for all the non-kernel event sources. The EOE would be the most
>>> seamless, but at a cost. My preference is to allow the 2 second 'timer'
>>> to be configurable.
>>
>> Agree with Burn, numbering the records coming up from the kernel is
>> going to be a real nightmare, and not something to consider lightly.
>> Especially when it sounds like we don't yet have a root cause for the
>> issue.
>
> A very long time ago, we had numbered records. But it was decided that
> there's no real point in it and we'd rather just save disk space.

With the current kernel code, adding numbered records is not something to take lightly.

> I know that the kernel does not serialize the events headed for user space.
> But I'm curious how an event gets stuck and others can jump ahead while one
> that's already inflight can get hung for 4 seconds before it's next record
> goes out?

Have you determined that the problem is the kernel? Initially it was looking like it was a userspace issue, is that no longer the general thought? Also, is there a reliable reproducer yet?

--
paul moore
www.paul-moore.com