* Nick Piggin <[EMAIL PROTECTED]> wrote: > Well in the context of a multi user system, this really is a > privileged operation. Witness: a normal user isn't even allowed to > raise the nice priority of a normal task. Note that I think everyone > agrees here, but I'm just repeating the point.
i've seen this argument repeated a number of times, but i'd like to point out that with the rlimit set to a sane value, a user can do 'less damage' to the system via SCHED_FIFO than it could do via nice--20! negative nice levels are a guaranteed way to monopolize the CPU. SCHED_FIFO with throttling could at most be used to 'steal' CPU time up to the threshold. Also, if a task 'runs away' in SCHED_FIFO mode it will be efficiently throttled. While if it 'runs away' in nice--20 mode, it will take away 95+% of the CPU time quite agressively. Furthermore, more nice--20 tasks will do much more damage (try thunk.c at nice--20!), while more throttled SCHED_FIFO tasks only do damage to their own class - the guaranteed share of SCHED_OTHER tasks (and privileged RT tasks) is not affected. so while it is true that in terms of priorities, throttled SCHED_FIFO trumps all SCHED_OTHER tasks, but in the "potential damage" sense, "throttled real-time" is less of a privilege than "nice--20". Ingo - 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/