Re: postgreSQL query via JDBC in different OS taking different running time?

On Mon, Oct 7, 2013 at 10:35 PM, Kevin Grittner <kgrittn(at)ymail(dot)com> wrote:
> Aftab Ahmed Chandio <aftabac(at)siat(dot)ac(dot)cn> wrote:
>
>> My query processes from JDBC (Java Program) to PostgreSQL. I use
>> system time by invoking java function, I collect one time unit
>> before the query statement perform and second after the execution
>> of query statement.
>> I found 85 ms time unit in DOS (win7) (laptop 4cores). both Java
>> and PostgreSQL installed and invoked on the same machine,
>> respectively.
>> On the other hand, I use same process (separate installation) on
>> linux on 8 cores physical machine with 2times greater then
>> laptop.
>> I found 150 ms. (which is a question for me because the time in
>> Linux environment should give me half of the time taking on
>> laptop)
>> I also make same setting of postgresql.conf in the linux setup,
>> which is available same in the win7 setup, because win7 setup
>> gives better performance of the query.
>> What do u suggest me, where I need to make performance tuning?
>> which configuration setting must need to modify in the linux?
>> * laptop RAM 4 GB and Linux machine 32 GB
>
> Given a little time, I could probably list 100 plausible reasons
> that could be. For my part, load balancing a production system
> between PostgreSQL on Windows and on Linux hitting identical
> databases on identical hardware, I saw 30% better performance on
> Linux.

One sneaky way that windows tends to beat linux is that windows has a
low precision high performance timer that linux does not have. This
affects both java and postgres and particularly tends to show up when
benchmarking with times.

merlin