Re: Selecting target CPU for thread
Nigel Wade wrote:
Daniel Pitts wrote:
On the other hand, the OS should know best on how to schedule
threads.
That isn't always the case, though. Probably the most likely instance where this
might not be true is HPC, where it's very important to ensure that threads are
making the maximum use of available CPU horsepower. After all, there's little
point in expending lots of effort and money building yourself a high-power
cluster only to find that the OS isn't sharing the load amongst the nodes
correctly, or is wasting CPU cycles by migrating threads unnecessarily,
resulting in time-wasting cache migration. Moving threads to different CPUs may
seem like a good idea to the OS, but a competent programmer well versed in
parallel programming might be able to do better. An OS is likely to be a
compromise.
Let your program's business be business logic.
If your programs business is only business logic perhaps, but if your programs
business is maximising the compute potential of an HPC then the criteria are
different.
"HPC"?
Where I work they process up to millions of documents per week during peak
periods, with a maximum size including XML this and compressed attachment that
of around 2 GB each. (Typical sizes are much smaller, tens to hundreds of
megabytes.)
Some of the Web servers have many CPUs (32 each is not unusual). They use
external monitoring tools (such as those marketed by IBM) to track CPU usage.
As Nigel and others have pointed out, you have to get outside the application
in order to monitor what resources are used outside the application.
--
Lew