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

Artem Belevich fbsdlist at src.cx
Sat Aug 28 03:34:19 UTC 2010

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:

> 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.


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


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