Re: CentOS - PostgreSQL 9.2.13 -> 9.4

Hi Melvin,

On 18/08/15 17:19, Melvin Davidson wrote:
>>8 x 16GB 1600MHz PC3-12800 DDR3 - 128GB total
> >>shared_buffers=60GB
>
> I would say 60GB is too high when you have 128GB system memory.
> Try lowering it to shared_buffers=32GB and let the O/S handle more of
> the work.
I have tested all different shared_buffers settings across both
versions, from 8GB - 60GB. 8-32GB were optimal. in reality the
difference from 8 - 32 was minimal.

>
>
> On Tue, Aug 18, 2015 at 11:49 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com
> <mailto:jeff(dot)janes(at)gmail(dot)com>> wrote:
>
> On Tue, Aug 18, 2015 at 8:01 AM, Michael H <michael(at)wemoto(dot)com
> <mailto:michael(at)wemoto(dot)com>> wrote:
>
> Hi,
>
> I've been tuning our new database server, here's some info...
>
> CentOS Linux release 7.1.1503 (Core)
> 3.10.0-229.11.1.el7.x86_64
>
> 8 x 16GB 1600MHz PC3-12800 DDR3 - 128GB total
> 2 x AMD Opteron 6386SE 2.8GHz/16-core/140w - 32 cores total
> 4 x 300GB SAS 10k HDD - raid 1+0
> configuration
> 1GB FBWC for P-series smart array - cache enabled
>
> I'm using the CentOS provided packages for PostgreSQL
> Version : 9.2.13
> Release : 1.el7_1
>
> I'm getting fairly good statistics from this server but after
> asking for some advice I was pointed towards PostgreSQL 9.3
> (posix memory management) and PostgreSQL 9.4 (pg_replication_slots).
>
> I dropped my original install of 9.2.13 above and went straight
> to the 9.4 from the PostgreSQL repositories.
>
>
>
> How did you get your data from 9.2 to 9.4? Did you run ANALYZE on
> it afterwards?
>
>
>
> Are there any known issues with my kernel and PostgreSQL? I
> found this post -
> http://www.databasesoup.com/2014/09/why-you-need-to-avoid-linux-kernel-32.html
>
> which states there are known issues up to kernel 3.10.. the
> reason I ask, no matter how small or big a configuration change
> I make I can't match my 9.2.13 install. I'm seeing huge
> decreases in TPS on all my benchmarks.
>
> for example, 9.2.13, my own extremely heavy SQL file being used
> here, hence the lower TPS...
>
> 32 37.357197
> 64 34.145088
> 128 19.682544
> 256 9.910772
> 512 5.803358
>
> compared to 9.4 - exactly the same tests and parameters
> configured (I also started from defaults and tuned up as best I
> could).
>
> 32 14.982111
> 64 14.894859
> 128 14.277631
> 256 13.679516
> 512 13.679516
>
>
> Pick the query that dropped in performance the most, then run it
> with "explain (analyze, buffers)" and with track_io_timing turned
> on, and compare this between the servers. Did the plan change, or
> just the time?
>
> Cheers,
>
> Jeff
>
>
>
>
> --
> *Melvin Davidson*
> I reserve the right to fantasize. Whether or not you
> wish to share my fantasy is entirely up to you.