Re: Question about speed: Weird Behavior

On Mon, 13 Jun 2011 14:12:24 -0300, Israel Ben Guilherme Fonseca wrote:
> Thanks for all the answers,
>
> Smogura: "This is system autotuning - a good solution."
>
> Where can I find more about this subject, and how can I weak it? Is
> it
> hidden on postresql.conf? Can I configure it to always use an specifc
> size like 8258 bytes per-package?
>
> Im doing tests on other drivers of other programming languages to
> postgresql, and for those, there wasnt any package size differences,
> only with the Java tests. Maybe the others drivers are setting
> specific values for this.
>
> 2011/6/13 Maciek Sakrejda
>
>>> There may be some GC
>> > overhead, you should call System.gc after or before each pass to
>> start with
>> > similar environment.
>>
>> Note that the contract of System.gc() is really more like "Hey, I
>> think it might be fun to run GC right now," than "Youll run GC
>> right
>> now and youll like it." In other words, its technically only a
>> suggestion, so you should make sure its actually doing something
>> before you start depending on it for performance numbers.
>>
>> ---
>> Maciek Sakrejda | System Architect | Truviso
>>
>> 1065 E. Hillsdale Blvd., Suite 215
>> Foster City, CA 94404
>> (650) 242-3500 Main
>> www.truviso.com [1]
>
>
>
> Links:
> ------
> [1] http://www.truviso.com
> [2] mailto:msakrejda(at)truviso(dot)com
Actually there is no way to tune it. On server side on Linux platforms
kernel will adjust send/recv buffer for you and it, in many situations,
does it good. On Windows I think this buffer (or send/recv) has fixed
size. You may try to change some Windows's registry settings, or proc
TCP/IP to decrease / increase max buffer size.

On Client side send/recv buffer should be auto tuned too, as Java uses
system sockets.

Of course, PGSQL internally has small buffer, as sockets doesn't use
TCP delay it size is 8k (I think it should be 16k).

I don't think it's good to manually tune this buffers (actually I done
two approaches for this), and system tuning is much more better.

If you are looking for some information about this search "TCP/IP
tuning" (you will get many how to determine good size of socket
recv/send buffers), and as well few links for kernel auto tuning.

Regards,
Radosław Smogura