[CFT] Improved ZFS metaslab code (faster write speed)

[Artem Belevich]

On Fri, Aug 27, 2010 at 6:24 PM, jhell <jhell at dataix.net> wrote:
> On 08/27/2010 19:50, Artem Belevich wrote:
>> Another "me too" here.
>>
>> 8-stable/amd64 + v15 (zpool still uses v14) + metaslab +
>> abe_stat_rrwlock + A.Gapon's vm_paging_needed() + uma defrag patches.
>>
>> The box survived few days of pounding on it without any signs of trouble.
>>
>
>        I must have missed the uma defrag patches but according to the code

Here is the UMA patch I was talking about:
http://unix.derkeiler.com/Mailing-Lists/FreeBSD/hackers/2010-08/msg00188.html

> those patches should not have any effect on your implimentation of ZFS
> on your system because vfs.zfs.zio.use_uma defaults to off unless you
> have manually turned this on or the patch reverts that facility back to
> its original form.

Hmm. Indeed. Kmem_malloc carves memory allocations directly from kmem.
Yet the difference in max ARC size with the patch applied is there.

http://unix.derkeiler.com/Mailing-Lists/FreeBSD/hackers/2010-08/msg00257.html

Perhaps reduced UMA fragmentation helps those subsystem that do use
UMA (including ZFS which always uses uma for various housekeeping
data).

--Artem