Hyperthreading slows down server

[javed74]

Hi Guys,

We just deployed our asp.net application on Xeon dual processor with
Hyperthreading turned on. OS Windows 2003 (Web Edition) .NET Framework
1.1

While stress testing with 1 wp, we get better throughput/RPS then with
enabling webGarden - 4 wps. Multiple worker processors with
Hyperthreading turned on gives approx. half the performance compared to
1 wp. As per my understanding results should be vice-versa.

Anybody having any information please let me know.

Thanks in advance.

-JA

 

[Bruce Barker]

this is correct. web gardens give greater stability at a performance cost.
this is because scheduling threads is cheaper than scheduling processes, and
thread context switches are cheaper than process context switches. also web
gardens are harder on the cpu caches (more cache misses).


-- bruce (sqlwork.com)

 

[Scott Allen]

Web gardens provide scalability increases for applications that have a
lot of resource contentions, like application locks and pages with
aspcompat="true". Anything else can be hit or miss.

 

[Scott Allen]

this is correct. web gardens give greater stability at a performance cost.
this is because scheduling threads is cheaper than scheduling processes, and
thread context switches are cheaper than process context switches. also web
gardens are harder on the cpu caches (more cache misses).

What does a "process contex switch" mean in Windows? How does giving a
process processor affinity cause more cache misses?