Thread

1. performance results on IBM POWER7

   Robert Haas <robertmhaas@gmail.com> — 2012-03-01T14:54:15Z

   IBM has provided the PostgreSQL community with access to a couple of
   IBM POWER7 machines through OSUOSL.  Simon has access to one, carved
   up into a couple of LPARs, for replication work, and there's a
   buildfarm animal on there as well, I think; I have access to the
   other, for performance testing.  I imagine we can get access for a few
   other people as well, though at the moment the performance-testing
   machine is inaccessible and I'm not having very much luck getting help
   from the very busy OSUOSL folks.  Anyway, before it bit the dust, I
   was able to do some basic pgbench tests at various scale factors and
   client counts.  I used my usual settings:
   
   shared_buffers = 8GB
   maintenance_work_mem = 1GB
   synchronous_commit = off
   checkpoint_segments = 300
   checkpoint_timeout = 15min
   checkpoint_completion_target = 0.9
   wal_writer_delay = 20ms
   
   I did three five-minute runs at each scale factors 100, 300, 1000,
   3000, and 10000, with varying client counts: 1, 2, and all multiples
   of 4 up to 80.  I stopped and restarted the database after each run
   (but did not flush the OS cache, so this is a warm-start test) and
   took the median of the three results for each run.  Full results are
   attached herewith; pretty graphs are on my blog at
   http://rhaas.blogspot.com/2012/03/performance-and-scalability-on-ibm.html
   
   When I get the machine back, my plan is to next run some read-write
   pgbench tests.  Those will need to be longer, though.  Read
   performance doesn't seem to be very sensitive to the length of the
   tests, but write performance is, so I'll probably need at least
   30-minute runs if not more to get an accurate sense of what the
   performance is like.  After that I think maybe some testing of the
   remaining CommitFest patches might be in order (though personally I'd
   like to wrap this CommitFest up fairly soon) to see if any of those
   improve things.
   
   -- 
   Robert Haas
   EnterpriseDB: http://www.enterprisedb.com
   The Enterprise PostgreSQL Company
   

2. Re: performance results on IBM POWER7

   Ants Aasma <ants.aasma@eesti.ee> — 2012-03-01T16:23:28Z

   On Thu, Mar 1, 2012 at 4:54 PM, Robert Haas <robertmhaas@gmail.com> wrote:
   > ... After that I think maybe some testing of the
   > remaining CommitFest patches might be in order (though personally I'd
   > like to wrap this CommitFest up fairly soon) to see if any of those
   > improve things.
   
   Besides performance testing, could you check how clocksources behave
   on this kind of machine?
   You can find pg_test_timing tool attached here:
   http://archives.postgresql.org/pgsql-hackers/2012-01/msg00937.php
   
   To see which clocksources are available, you can do:
   # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
   To switch the clocksource, just write the desired clocksource like this:
   # echo hpet > /sys/devices/system/clocksource/clocksource0/current_clocksource
   
   Thanks,
   Ants Aasma
   
   

3. Re: performance results on IBM POWER7

   Robert Haas <robertmhaas@gmail.com> — 2012-03-01T16:38:42Z

   On Thu, Mar 1, 2012 at 11:23 AM, Ants Aasma <ants.aasma@eesti.ee> wrote:
   > On Thu, Mar 1, 2012 at 4:54 PM, Robert Haas <robertmhaas@gmail.com> wrote:
   >> ... After that I think maybe some testing of the
   >> remaining CommitFest patches might be in order (though personally I'd
   >> like to wrap this CommitFest up fairly soon) to see if any of those
   >> improve things.
   >
   > Besides performance testing, could you check how clocksources behave
   > on this kind of machine?
   > You can find pg_test_timing tool attached here:
   > http://archives.postgresql.org/pgsql-hackers/2012-01/msg00937.php
   >
   > To see which clocksources are available, you can do:
   > # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
   > To switch the clocksource, just write the desired clocksource like this:
   > # echo hpet > /sys/devices/system/clocksource/clocksource0/current_clocksource
   
   Sure, I'll check that as soon as it's back up.
   
   -- 
   Robert Haas
   EnterpriseDB: http://www.enterprisedb.com
   The Enterprise PostgreSQL Company
   
   

4. Re: performance results on IBM POWER7

   Robert Haas <robertmhaas@gmail.com> — 2012-03-05T18:26:59Z

   On Thu, Mar 1, 2012 at 11:38 AM, Robert Haas <robertmhaas@gmail.com> wrote:
   > On Thu, Mar 1, 2012 at 11:23 AM, Ants Aasma <ants.aasma@eesti.ee> wrote:
   >> On Thu, Mar 1, 2012 at 4:54 PM, Robert Haas <robertmhaas@gmail.com> wrote:
   >>> ... After that I think maybe some testing of the
   >>> remaining CommitFest patches might be in order (though personally I'd
   >>> like to wrap this CommitFest up fairly soon) to see if any of those
   >>> improve things.
   >>
   >> Besides performance testing, could you check how clocksources behave
   >> on this kind of machine?
   >> You can find pg_test_timing tool attached here:
   >> http://archives.postgresql.org/pgsql-hackers/2012-01/msg00937.php
   >>
   >> To see which clocksources are available, you can do:
   >> # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
   >> To switch the clocksource, just write the desired clocksource like this:
   >> # echo hpet > /sys/devices/system/clocksource/clocksource0/current_clocksource
   >
   > Sure, I'll check that as soon as it's back up.
   
   It seems that "timebase" is the only available clock source.
   pg_test_timing says:
   
   Testing timing overhead for 3 seconds.
   Per timing duration including loop overhead: 38.47 ns
   Histogram of timing durations:
      < usec:      count   percent
          32:          6  0.00001%
          16:          4  0.00001%
           8:          8  0.00001%
           4:        282  0.00036%
           2:    2999189  3.84628%
           1:   74976816 96.15333%
   
   -- 
   Robert Haas
   EnterpriseDB: http://www.enterprisedb.com
   The Enterprise PostgreSQL Company