Date: Tue, 6 Dec 2016 21:01:04 +0000 From: Steven Hartland <killing@multiplay.co.uk> To: freebsd-fs@freebsd.org Subject: Re: 11-STABLE vs 11.0-RELENG test Message-ID: <fa10ebb4-3d1d-02f9-d816-88f7d55cd8a1@multiplay.co.uk> In-Reply-To: <8b4ba98d-03d3-f671-33b2-ed12d3b4fb7c@FreeBSD.org> References: <8b4ba98d-03d3-f671-33b2-ed12d3b4fb7c@FreeBSD.org>
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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.
>
Other sysctls which may have an impact are:
vfs.zfs.vdev.async_write_max_active
vfs.zfs.vdev.queue_depth_pct
Regards
Steve
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