Questions[multi-threading](server)

I'm not sure whether serverfault is the right place to ask this, but I wonder what choice you would make if you had to select a new CPU type for your Java Web Application:

a) a CPU with 32 cores and clock speed 2.5 Ghz

or

b) a CPU with 8 cores but clock speed of 3.8 Ghz

Given the fact that each of the web application's incoming HTTP request is served by a free Java thread, it might make sense to choose a), because you can process four time more HTTP requests at the same time. However, on the other hand, CPU b) can finish the processing of a single HTTP request much faster...

What do you think?

Sidenotes:

• it has to be a physical machine, VMs or cloud solutions are not an option in this case
• RAM is not important, the server will have 512GB of RAM in the end
• Caching: the Java web application features an extensive caching framework, so the choice is really on the CPUs.

Running multiple scp threads simultaneously:

Background:

I'm often finding myself mirroring a set of server files a lot, and included in these server files are thousands of little 1kb-3kb files. All the servers are connected to 1Gbps ports, generally spread out in a variety of data-centers.

Problem:

SCP transfers these little files, ONE by ONE, and it takes ages, and I feel like I'm wasting the beautiful network resources I have.

Solution?:

I had an idea; Creating a script, which divides the files up into equal amounts, and starts up 5-6 scp threads, which theoretically would then get done 5-6 times faster, no? But I don't have any linux scripting experience!

Question(s):

• Is there a better solution to the mentioned problem?
• Is there something like this that exists already?
• If not, is there someone who would give me a start, or help me out?
• If not to 2, or 3, where would be a good place to start looking to learn linux scripting? Like bash, or other.

When I renice a multithreaded process in Ubuntu 10.04, then view the results in top, it seems that only the main thread actually gets reniced. All the other threads retain their old nice value. What's the easiest way to renice all threads in a process instead of just the main thread?

I have quad core CPU with hyper threading enabled. So I have 8 logical cores. I want to limit my application to use only 4 cores and I want this 4 cores to be different physical cores. Which taskset options (core numbers) should I use? :

• taskset -c 0,1,2,3 command or
• taskset -c 0,2,4,6 command

Thank you.

Let's say I have a quad-core box and four identical processes, each with ten threads. Is it possible, in Linux, to say that Process A is only allowed to run on CPU 0, Process B is only allowed to run on CPU 1, etc?