Change uma_mtx to rwlock

[Bryan Venteicher]

On Sat, Sep 27, 2014 at 9:30 PM, Steven Hartland <killing at multiplay.co.uk>
wrote:

> ----- Original Message ----- From: "Bryan Venteicher" <
> bryanv at daemoninthecloset.org>
>
>> On Sat, Sep 27, 2014 at 8:42 PM, Steven Hartland <killing at multiplay.co.uk
>> >
>> wrote:
>>
>>  Out of interest does that include ZFS and its UMA zones, as we're
>>> currently
>>> investigating issues around this.
>>>
>>>
>>>  Yes, I believe this would include ZFS's zones too
>>
>
> It would but I was more curious as it if you had seen the delay
> specifically on
> the ZFS zone or if it was other zones which triggered the issue for you?
>
>
​We are using an old version of FreeBSD/ZFS, so our ZFS allocations go
through malloc instead of directly to UMA.

For us, it was the cumulative effect of the number of UMA zones (buckets
really) ​that lead to long hold times of the UMA mutex. ZFS related
allocations were a significant part of that, but not typically the largest.



>    Regards
>    Steve
>