Re: Fwd: Help！Why CPU Usage and LoadAverage Jump up Suddenly

On 12/6/2013 11:04 AM, 吕晓旭 wrote:
> I find something with top : CPU usage of each postgres process is not
> so high when low concurrency, the highest one is about 50%.
> but when concurrency gradually increased, some postgres process cpu
> usage reach 100%, and keep a moment. and at these high concurrency
> period runq-sz(with sar -q) is very long, sometime 50 process waiting
> the CPU time.
> so is there something like spin-lock keep the CPU time?
>
>
> some configurations on the both system:
> shared_buffers = 8192MB
> work_mem =256MB
> maintenance_work_mem = 160MB
> full_page_writes = off
> wal_buffers = 10MB
> wal_keep_segments = 150

50 concurrent active queries with work_mem = 256MB would use like 13GB
ram, or possibly more if the queries are complex and require multiple
work_mems. I see you have 64GB ram on the 'slow' system, so that
/shouldn't/ be an issue, unless you end up with much higher concurrent
query counts.

seems to be a lot of variables here, one system is running CentOS 5.x
and the other CentOS 6.x, if I remember correctly from your first post.
different memory sizes. different disk controllers. both CentOS
versions are quite out of date (5.7 and 6.5 are both direct inplace
upgrades). I also recall CentOS 6.2 had some file system bugs
relating to XFS, but I dunno if that applies here. hmmmm, kernel 3.2.34
? thats not the centos 6.2 kernel, where is it from ?

btw, those CPUs have 12 threads, not 24

--
john r pierce 37N 122W
somewhere on the middle of the left coast