Re: amrd disk performance drop after running under high load

Alexey Popov wrote:

After some time of running under high load disk performance become expremely poor. At that periods 'systat -vm 1' shows something like this:

What does "high load" mean? You need to explain the system workload more.

Disks amrd0
KB/t 85.39
tps 5
MB/s 0.38
% busy 99

Apart of all, I tried to make mutex profiling and here's the results (sorted by the total number of acquisitions):

Bad case:

102 223514 273977 0 14689 1651568 /usr/src/sys/vm/uma_core.c:2349 (512)
950 263099 273968 0 15004 14427 /usr/src/sys/vm/uma_core.c:2450 (512)
108 150422 175840 0 10978 22988519 /usr/src/sys/vm/uma_core.c:1888 (mbuf)

> Here you can see that high UMA activity happens in periods of low disk
> performance. But I'm not sure whether this is a root of the problem, not
> a consequence.

The extremely high contention there does seem to say you have a mbuf starvation problem and not a disk problem. I don't know why this would be happening off-hand.

Can you also provide more details about the system hardware and configuration?

Kris



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