Messages in this thread | | | Subject | Re: [RFC] [PATCH] Pre-emption control for userspace | From | Davidlohr Bueso <> | Date | Mon, 03 Mar 2014 13:51:33 -0800 |
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On Mon, 2014-03-03 at 11:07 -0700, Khalid Aziz wrote: > I am working on a feature that has been requested by database folks that > helps with performance. Some of the oft executed database code uses > mutexes to lock other threads out of a critical section. They often see > a situation where a thread grabs the mutex, runs out of its timeslice > and gets switched out which then causes another thread to run which > tries to grab the same mutex, spins for a while and finally gives up.
This strikes me more of a feature for a real-time kernel. It is definitely an interesting concept but wonder about it being abused. Also, what about just using a voluntary preemption model instead? I'd think that systems where this is really a problem would opt for that.
> This can happen with multiple threads until original lock owner gets the > CPU again and can complete executing its critical section. This queueing > and subsequent CPU cycle wastage can be avoided if the locking thread > could request to be granted an additional timeslice if its current > timeslice runs out before it gives up the lock. Other operating systems > have implemented this functionality and is used by databases as well as > JVM. This functionality has been shown to improve performance by 3%-5%.
Could you elaborate more on those performance numbers? What benchmark/workload?
Thanks, Davidlohr
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