Re: [PATCH v3] sched/fair: Add advisory flag for borrowing a timeslice

[Khalid Aziz]

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/