Re: CentOS - PostgreSQL 9.2.13 -> 9.4

On Tue, Aug 18, 2015 at 8:01 AM, Michael H <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