Messages in this thread | | | Date | Tue, 25 Nov 2014 07:52:25 -0700 | From | Khalid Aziz <> | Subject | Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice |
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On 11/24/2014 07:03 PM, Rik van Riel wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 11/24/2014 03:56 PM, Khalid Aziz wrote: >> sched/fair: Add advisory flag for borrowing a timeslice >> >> This patch adds a way for a task to request to borrow one >> timeslice from future if it is about to be preempted, so it could >> delay preemption and complete any critical task it is in the middle >> of. >> >> This feature helps with performance on databases and has been used >> for many years on other OSs by the databases. This feature helps in >> situation where a task acquires a lock before performing a critical >> operation on the database and happens to get preempted > > Why don't the other tasks that want the lock sleep on the > lock? > > I can see this "solution" help mostly with userspace spinlocks, > which are relics of a past era that need to die. There is no > way userspace spinlocks will not fail miserably on virtual > machines, and it is time to get rid of them.
This solution indeed is for userspace spinlocks. Database code has been written with all critical locking implemented in userspace (as I have been told by database folks. I am not a database guy).
-- Khalid
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