Date: Tue, 16 May 2006 14:19:47 +0100
From: "Jignesh K. Shah" <J.K.Shah@Sun.COM>
Subject: Re: Pgsql (and mysql) benchmark on T2000/Solaris and some
In-reply-to: <44699C6C.80302@tweakers.net>
To: Arjen van der Meijden <acmmailing@tweakers.net>
Cc: pgsql-performance <pgsql-performance@postgresql.org>
Message-id: <4469D173.50406@sun.com>
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Hi Arjen,

Looking at your outputs...of syscall and usrcall it looks like

* Spending too much time in semsys .... which means you have too many 
connections and they are contending to get a lock.. which is potentially 
the WAL log lock


* llseek is high which means you can obviously gain a bit with the right 
file system/files tuning by caching them right.


Have you set the values for Solaris for T2000 tuned for Postgresql?

Check out the tunables from the following URL

http://www.sun.com/servers/coolthreads/tnb/applications_postgresql.jsp

Try specially the /etc/system and postgresql.conf changes  and see if it 
changes/improves your performance.


Regards,
Jignesh


Arjen van der Meijden wrote:
> Hi List,
> 
> In the past few weeks we have been developing a read-heavy 
> mysql-benchmark to have an alternative take at cpu/platform-performance. 
> Not really to have a look at how fast mysql can be.
> 
> This benchmark runs on mysql 4.1.x, 5.0.x and 5.1.x and is modelled 
> after our website's production database and the load generated on it is 
> modelled after a simplified version of our visitor behaviour.
> 
> Long story short, we think the test is a nice example of the relatively 
> lightweight, read-heavy webapplications out there and therefore decided 
> to have a go at postgresql as well.
> Of course the queries and indexes have been adjusted to (by our 
> knowledge) best suit postgresql, while maintaining the same output to 
> the application/interface layer. While the initial structure only got 
> postgresql at about half the performance of mysql 4.1.x, the current 
> version of our postgresql-benchmark has quite similar results to mysql 
> 4.1.x, but both are quite a bit slower than 5.0.x (I think its about 
> 30-40% faster).
> 
> Since the results from those benchmarks are not yet public (they will be 
> put together in a story at our website), I won't go into too much 
> details about this benchmark.
> 
> Currently we're having a look at a Sun T2000 and will be looking at will 
> be looking at other machines as well in the future. We are running the 
> sun-release of postgresql 8.1.3 on that T2000 now, but are looking at 
> compiling the cvs-head version (for its index-root-cache) somewhere this 
> week.
> 
> My guess is there are a few people on this list who are interested in 
> some dtrace results taken during our benchmarks on that T2000.
> Although my knowledge of both Solaris and Dtrace are very limited, I 
> already took some samples of the system and user calls. I used Jignesh 
> Shah's scripts for that: 
> http://blogs.sun.com/roller/page/jkshah?entry=profiling_postgresql_using_dtrace_on 
> 
> 
> You can find the samples here:
> http://achelois.tweakers.net/~acm/pgsql-t2000/syscall.log
> http://achelois.tweakers.net/~acm/pgsql-t2000/usrcall.log
> 
> And I also did the memcpy-scripts, here:
> http://achelois.tweakers.net/~acm/pgsql-t2000/memcpysize.log
> http://achelois.tweakers.net/~acm/pgsql-t2000/memcpystack.log
> (this last log is 3.5MB)
> 
> If anyone is interested in some more dtrace results, let me know (and 
> tell me what commands to run ;-) ).
> 
> Best regards,
> 
> Arjen
> 
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