Re: [PERFORM] About “context-switching issue on Xeon” test case ？

2010/4/9 Greg Smith <greg(at)2ndquadrant(dot)com>:
> RD黄永卫 wrote:
>>
>> Anybody have the test case of “ context-switching issue on Xeon” from
>> Tm lane ？
>>
>
> That takes me back:
> http://archives.postgresql.org/pgsql-performance/2004-04/msg00280.php
>
> That's a problem seen on 2004 era Xeon processors, and with PostgreSQL
> 7.4. I doubt it has much relevance nowadays, given a) that whole area of
> the code was rewritten for PostgreSQL 8.1, and b) today's Xeons are
> nothing like 2004's Xeons.

It's important to appreciate that all improvements in scalability for
xeons, opterons, and everything else has mostly just moved further
along to the right on the graph where you start doing more context
switching than work, and the performance falls off. The same way that
(sometimes) throwing more cores at a problem can help. For most
office sized pgsql servers there's still a real possibility of having
a machine getting slammed and one of the indicators of that is that
context switches per second will start to jump up and the machine gets
sluggish.

For 2 sockets Intel rules the roost. I'd imagine AMD's much faster
bus architecture for >2 sockets would make them the winner, but I
haven't had a system like that to test, either Intel or AMD.