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I progressed with testing a bit further and found that I was hitting
another scheduling bottleneck - the network. While the write burst was
running and ZFS was commiting data to disk, the server was dropping
incomming UDP packets ("netstat -s | grep udpInOverflows" grew by about
1000-2000 packets during every write burst).
To work around that I had to boost the scheduling priority of recorder
processes to the real-time class and I also had to lower
zfs_txg_timeout=1 (there was still minor packet drop after just doing
priocntl on the processes) to even out the CPU load.
Any ideas on why ZFS should completely thrash the network layer and make
it drop incomming packets?
Regards,
- --
Saso
Robert Milkowski wrote:
> On 26/12/2009 12:22, Saso Kiselkov wrote:
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>> Thank you, the post you mentioned helped me move a bit forward. I tried
>> putting:
>>
>> zfs:zfs_txg_timeout = 1
> btw: you can tune it on a live system without a need to do reboots.
>
> mi...@r600:~# echo zfs_txg_timeout/D | mdb -k
> zfs_txg_timeout:
> zfs_txg_timeout:30
> mi...@r600:~# echo zfs_txg_timeout/W0t1 | mdb -kw
> zfs_txg_timeout:0x1e = 0x1
> mi...@r600:~# echo zfs_txg_timeout/D | mdb -k
> zfs_txg_timeout:
> zfs_txg_timeout:1
> mi...@r600:~# echo zfs_txg_timeout/W0t30 | mdb -kw
> zfs_txg_timeout:0x1 = 0x1e
> mi...@r600:~# echo zfs_txg_timeout/D | mdb -k
> zfs_txg_timeout:
> zfs_txg_timeout:30
> mi...@r600:~#
>
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