Re:Not 100,000 threads in parallel, just 50. (Score 4, Informative)

Apache 2.0 doesn't actually do thread creation very frequently. The thread creation cost occurs mostly at startup. So the limiting factors for threaded Apache performance on Linux are mainly:

• The speed with which the kernel can schedule and context-switch among threads
  For some recent data on this, see http://marc.theaimsgroup.com/?l=apache-httpd-dev&m =103228014211983. The O(1) scheduler patch for 2.4 seems to help here.
• Memory usage per thread
• Concurrency limitations of the Apache code itself
  This has been improving gradually with successive 2.0 releases, as the remaining global locks are removed or optimized.
• General robustness of the thread implementation
  The current (2.4) Linux threading implementation doesn't work well with debuggers.

At first glance, it looks like the NPTL could be a win for threaded Apache on Linux, as offers some solutions first the first and last of these issues.