Re: [PATCH v3] kernel/module: Reschedule while waiting for modules to finish loading

[Jessica Yu]

+++ Prarit Bhargava [01/05/19 17:26 -0400]:
> On 4/30/19 6:22 PM, Prarit Bhargava wrote:
> > On a s390 z14 LAR with 2 cpus about stalls about 3% of the time while
> > loading the s390_trng.ko module.
> >
> > Add a reschedule point to the loop that waits for modules to complete
> > loading.
> >
> > v3: cleanup Fixes line.
>
> Jessica, even with this additional patch there appears to be some other issues
> in the module code that are causing significant delays in boot up on large
> systems.

Is this limited to only s390? Or are you seeing this on other arches
as well? And is it limited to specific modules (like s390_trng)?

> Please revert these fixes from linux-next & modules-next.  I apologize for the
> extra work but I think it is for the best until I come up with a more complete &
> better tested patch.

Sure, then I will revert this patch and the other one as well
("modules: Only return -EEXIST for modules that have finished
loading").

> FWIW, the logic in the original patch is correct.  It's just that there's, as
> Heiko discovered, some poor scheduling, etc., that is impacting the module
> loading code after these changes.

I am really curious to see what these performance regressions look
like :/ Please update us when you find out more.

> Again, my apologies,

No problem! Thanks again.

Jessica