Re: zLinux Load Testing Experience

On Tue, Apr 30, 2013 at 8:28 AM, Andrew Hastie <andrew(at)ahastie(dot)net> wrote:

> I'm currently working on a project porting an application from RedHat
> Linux on Intel onto IBM zLinux. Our application requires PostgreSQL at
> version 9.n, so the PostgreSQL binaries have been built using the standard
> build tools from source. Everything appears run correctly. However as part
> of performance testing, our IBM and Linux SysProgs have been "poking
> around" using strace and have reported the following (which they think is
> an error condition) when hooking up to the postmaster processes:-
>
> read(3, 0x3ffff875ee0, 16) = -1 EAGAIN (Resource temporarily unavailable)
> poll([{fd=3, events=POLLIN}, {fd=6, events=POLLIN}], 2, 200) = 0 (Timeout)
> read(3, 0x3ffff875ee0, 16) = -1 EAGAIN (Resource temporarily unavailable)
> poll([{fd=3, events=POLLIN}, {fd=6, events=POLLIN}], 2, 10000) = 0
> (Timeout)
> ... repeated many times
>
>

That does not look like the postmaster process. It looks like probably the
background writer process.

It is normal, and doesn't explain high CPU utilization.

Cheers,

Jeff