On 11/25/2014 09:52 AM, Khalid Aziz wrote: > 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). They should fix that. The scheme you propose can really only work on bare metal, and not on virtual machines. That improves the problem for, what, 60% of new installs (and dropping)? -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
