[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-devel] Re: [RFC][PATCH] Scheduler interface changes for credit2


  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
  • Date: Mon, 22 Feb 2010 15:22:03 +0000
  • Cc: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Delivery-date: Mon, 22 Feb 2010 07:22:37 -0800
  • Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=QwmegX4fYXLgqosGicj2wtKu5Sv3pp2ZaE3z4IL37MeAETxjQhX6PRBYyryIAUDZNg XzZPRRlqrwnfQWLfZNRu1QpAQL2+u8CNTmgO9xhQZWWD/SXBjbidY0uutXsLJ8tpWWIQ ZCr12bWheYGqbedWz7Tkdz80yn045Orhpvbmk=
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Keir, any thoughts?  Does this seem like a reasonable approach?

Thanks,
 -George

On Mon, Feb 15, 2010 at 5:20 PM, George Dunlap
<George.Dunlap@xxxxxxxxxxxxx> wrote:
> The two attached patches change the scheduler interface to allow
> credit2 to have several cpus share the same runqueue.  The patches
> should have almost no impact on the current schedulers.  The patches
> and their reasonings are below.  I've also attached the patches for
> the prototype credit2 scheduler, for reference.
>
> * Add a context swich callback (sched-context_switch-callback.diff)
>
> Add a callback to tell a scheduler that a vcpu has been completely
> context-switched off a cpu.
>
> When sharing a runqueue, we can't put a scheduled-out vcpu back on the
> runqueue until it's been completely de-scheduled, because it may be
> grabbed by another processor before it's ready.  This callback allows
> a scheduler to detect when a vcpu on its way out is completely off the
> processor, so that it can put the vcpu on the runqueue.
>
> * Allow sharing of locks between cpus (sched-spin_lock-pointers.diff)
>
> Have per-cpu pointers, initialized to per-cpu locks, which the
> scheduler may change during its init to reconfigure locking
> granularity.
>
> There are a number of race conditions having to do with updating of
> v->is_running and v->processor, all having to do with the fact that
> vcpus may change cpus without an explicit migrate.  Furthermore, the
> scheduler needs runqueues to be covered by a lock as well.  The
> cleanest way to solve all of these is to have the scheduler lock and
> the runqueue lock coincide.
>
> * Add a "scheduler" trace class (trace-sched-class.diff)
> Uses defined on a per-scheduler basis
>
> I've been running parallel kernel compiles on a 16-way box (2x4x2) for
> several hours now without deadlocks or BUG()s.  As far as I'm
> concerned, with these changes, credit2 is now ready to be checked in,
> as long as it's not set to the default scheduler.
>
> All of the above:
> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
>

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.