Freebsd 11.0 - system freeze on intensive I/O

[Gautam]

Hi,

On Sat, Aug 12, 2017 at 8:53 PM, Warner Losh <imp at bsdimp.com> wrote:

>
>
> On Fri, Aug 11, 2017 at 11:17 PM, Gautam <list at execve.net> wrote:
>
>> > ​One update on this one. I installed a custom stable/11 kernel and world
>> (sched = 4BSD was the only change), and the problem
>> is no longer seen. From my untrained eyes, it looks like some kind of swap
>> request starvation causing a hang when ULE is in use.​
>>
>
> I did some patches a few years ago that separated out geom requests into
> their own uma map, if you wanted and hacked the swap pager to use that to
> ensure that it always had BIOs available to do it's I/O. Maybe I should
> dust them off and see if they help you. They didn't seem to help me too
> much, but didn't hurt too much either.
>
> There's still the issue of some drivers not pre-allocating requests, which
> is what makes the deadlock possible in the first place.
>
> Warner
>
>
I would be willing to try the patches and report back - although my
understanding of FreeBSD inter​nals is next to zero; but can surely try.

​Thanks,
Gautam
​