11-STABLE vs 11.0-RELENG test

[Steven Hartland]

On 06/12/2016 20:26, Alexander Motin wrote:
> On 06/12/2016 18:17, Alex Tutubalin wrote:
>> Followup, same box as in 1st message, but with different HBA and 5 HDD:
>>
>> Summary:
>>   1) read speed depends on 'on-disk' data, not by code used while read.
>>   2) FreeBSD 11.0-releng (svn up today) creates 'fast' big files (420+
> Mb/s read
>> speed)
>>   3)  FreeBSD 11-STABLE creates 'slow' big files. (~200  Mb/s)
>>   4) zfs send slow-dataset | zfs recv   (under 11.0-releng) creates
>> 'intermediate' files (320Mb/s)
>>   5) file copy slow-file ... (under 11.0-releng) creates fast copy
> (400+Mb/s)
>> So, ZFS write code in 11-STABLE looks broken.
> I've reproduced this issue with quick test on my lab system configured
> with 12-disk RAIDZ2 pool.  I've measured write and read back (with and
> without prefetch) speeds for pool recreated on different FreeBSD head
> revisions:
> 		r309625	r305456	r305330	r305322
> write		702	701	1115	1120
> read w/ pref	232	228	518	512
> read w/o pref	128	126	242	240
>
> I suspect we could obtain the problem here:
>
> r305331 | mav | 2016-09-03 13:04:37 +0300 (сб, 03 сент. 2016) | 45 lines
>
> MFV r304155: 7090 zfs should improve allocation order and throttle
> allocations
>
> I'll take closer look on that change tomorrow.
>
Does setting vfs.zfs.zio.dva_throttle_enabled=0 fix / improve performance?

     Regards
     Steve