Re: zLinux Load Testing Experience

On Wed, May 1, 2013 at 8:01 AM, Andrew Hastie <andrew(at)ahastie(dot)net> wrote:
>
> On 30/04/13 20:46, Merlin Moncure wrote:
>>
>> On Tue, Apr 30, 2013 at 12:26 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>>>
>>> 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.
>>
>> yeah: we're probably a couple of steps in front of deep system
>> profiling. Helpful things to provide to help diagnose would be:
>>
>> *) 'explain analyze' of the queries that are eating cpu
>> *) more details about the hardware -- how many cpu, etc.
>> *) better definition of 'perceived high CPU utilisation'
>> *) some correlating performance tests, expecially cpu bound pgbench
>> tests (pgbench -S)
>>
>> merlin
>>
>>
> I'm not sure how much experience the community has on tuning PostgreSQL
> running on RedHat which in turn is hosted on an IBM mainframe under VM
> (using zLinux). So I'm happy to start posting further details and benchmark
> results and see where we go. Should I be moving this thread over into the
> pg-performance list, or is pg-general the right place?

certainly performance. and yes, zLinux is less well traveled. Did
you compile postgres from source? Did you confirm that there is a
native spinlocks implementation and it is being used?

merlin