Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice (was: Pre-emption control for userspace)

[Rik van Riel]

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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.

- -- 
All rights reversed
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