Re: amrd disk performance drop after running under high load
- From: Kris Kennaway <kris@xxxxxxxxxxx>
- Date: Tue, 16 Oct 2007 11:03:05 +0200
Alexey Popov wrote:
Hi.
Kris Kennaway wrote:
This web service is similiar to YouTube. This server is video store. IAfter 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.
have around 200G of *.flv (flash video) files on the server.
I run lighttpd as a web server. Disk load is usually around 50%, network
output 100Mbit/s, 100 simultaneous connections. CPU is mostly idle.
As you can see it is a trivial service - sending files to network via HTTP.
A couple of comments.
Does lighttpd actually use HTTP accept filters?
Are you using ipfilter and ipfw? You are paying a performance penalty for having them.
You might try increasing BUCKET_MAX in sys/vm/uma_core.c. I don't really understand the code here, but you seem to be hitting a threshold behaviour where you are constantly running out of space in the per CPU caches.
This can happen if your workload is unbalanced between the CPUs and you are always allocating on one but freeing on another, but I wouldn't expect it should happen on your workload. Maybe it can also happen if your turnover is high enough. What does vmstat -z show during the good and bad times?
Kris
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