Re: zLinux Load Testing Experience

On 01/05/13 15:34, Merlin Moncure wrote:
> 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
>
Did you compile postgres from source? - Yes (I need PG v9.n as v8.n
shipped with RedHat Ent6 does not have several v9 specific features we
need).

Did you confirm that there is a native spinlocks implementation and it is being used? - I believe so as no errors or warnings logged during the build. Is there a simple way to check whether spin-locks are running native?

I've started looking at several articles covering pgbench and running some initial tests, so I plan to start a new thread on pg-performance in the next day or so.

Thanks for the advice so far - Appreciated :-)

Andrew