> I didn't suggest adding any unfairness! I suggested being fair by > user/job/process instead of being fair by thread (which is actually > unfair as it favors multi threaded processes over single threaded > processes).
Wouldn't that be unfair because it favors multi-user approaches over single-user approaches with the same number of processes? Consider two otherwise equivalent web server designs. They both use a helper process owned by the user who owns the file the web server is sending. One does a lot of work in the helper process, the other does very little. A "fair by user" scheduler would give the approach that puts more work in the helper process more CPU than the one that puts little work in the helper process. Being fair by user builds lots of assumptions into the scheduler. When they're not true, the scheduler becomes sub-optimal. For example, consider a web server that runs two very important tools, 'foo' and 'bar'. Rather than running them as root, they run as users 'foo' and 'bar' for security. "Fair to user" would mean that just because most other people are using 'foo', I get less CPU when I try to use 'foo', because the OS doesn't know the "real user", just the fake user who owns the process -- a security decision that has no relationship to fairness. This would be handled perfectly by a "fair to process" approach. As for favoring multi-threaded processes over single-threaded processes, sometimes that's what you want. Consider two servers, one using thread per job the other using process per job. Does it make sense to give the "process per job" server as much CPU to do a single task as the "thread per job" server gets for all the clients it's dealing with? It's really more important that the scheduler be tunable and predictable. That way, we can tell it what we want and get it. But the scheduler cannot read our minds. DS - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
