hi z_wr_iss while copying to non compressed drive #3077
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this editor is weird.... |
behlendorf
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the
Type: Performance
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me too; |
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If you could run |
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@behlendorf correct me if i'm wrong (I am not a programmer) the if yes, why isn't the raidz type parsed at import time and then call directly the corresponding function like vdev_raidz_generate_parity_p / vdev_raidz_generate_parity_pq / vdev_raidz_generate_parity_pqr ? |
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referencing #3374 |
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@mailinglists35 tour close but there's some subtlety here. The stats show that we're spending a lot of time in Disabling the compression entirely disables the zero detection which would normally automatically convert these zeros to a hole. See Exactly what behavior were you expecting to get when disabling compression? |
By disabling compression I expected the quantity of input data fed by dd into a file to match the data actually written on disk, in order to measure the array performance for sequential writes. I find sequential writes a bit slow on raidz3 despite the fact that the storage can withstand much greater values so I suspected that I am cpu bound; however I am unsure whether the CPU is really too slow for raidz3 calculations or the parity calculation routines could be improved. |
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It definitely does look like your CPU bound and there is certainly room for performance improvements in the parity calculations. :) |
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From a support standpoint, I would suggest checking that CPU throttling is disabled and your CPUs are actually running at full speed. You might be able to buy a bit more performance from it. |
cpu stays at max frequency: How do I check for throttling? All I see is this: and PS: Hyperthreading is disabled. |
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I’m also seeing this while transforming a VM template into a VM. So, it’s a 10G data copy from the pool to itself. The pool is almost empty (1.6T free, 2G total). |
note to self: |
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this is still happening in 0.8.0-rc1 (rpm from zfs-test repo) on a pretty modern hardware and decent kernel version (oracle linux uek 4.1) |
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perf report zoom on the one with "self" column at 28% CPU |
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and the next two with 9%: most other small end up also in |
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I've a similar issue, I've a high load if I do some writes to the volume via iscsi (LIO) and its mostly osq_lock. I've an Intel E5-2640 v4, 256GB RAM
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This issue has been automatically marked as "stale" because it has not had any activity for a while. It will be closed in 90 days if no further activity occurs. Thank you for your contributions. |
and others
While copying a large file to a volume that was not compressed the z_wr_iss still maxed out.
This is iotop:
This is the layout of the zfs
I was copying to zdata/media over samba
This is the layout:
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