|
xen-devel
[Xen-devel] Re: [PATCH RFC V5 00/11] Paravirtualized ticketlocks
|
To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|
Subject: |
[Xen-devel] Re: [PATCH RFC V5 00/11] Paravirtualized ticketlocks |
|
From: |
Peter Zijlstra <peterz@xxxxxxxxxxxxx> |
|
Date: |
Thu, 13 Oct 2011 12:54:05 +0200 |
|
Cc: |
Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Marcelo Tosatti <mtosatti@xxxxxxxxxx>, Nick Piggin <npiggin@xxxxxxxxx>, KVM <kvm@xxxxxxxxxxxxxxx>, maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Andi Kleen <andi@xxxxxxxxxxxxxx>, Avi Kivity <avi@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, the |
|
Delivery-date: |
Thu, 13 Oct 2011 03:58:20 -0700 |
|
Envelope-to: |
www-data@xxxxxxxxxxxxxxxxxxx |
|
In-reply-to: |
<cover.1318466916.git.jeremy.fitzhardinge@xxxxxxxxxx> |
|
List-help: |
<mailto:xen-devel-request@lists.xensource.com?subject=help> |
|
List-id: |
Xen developer discussion <xen-devel.lists.xensource.com> |
|
List-post: |
<mailto:xen-devel@lists.xensource.com> |
|
List-subscribe: |
<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe> |
|
List-unsubscribe: |
<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe> |
|
References: |
<cover.1318466916.git.jeremy.fitzhardinge@xxxxxxxxxx> |
|
Sender: |
xen-devel-bounces@xxxxxxxxxxxxxxxxxxx |
On Wed, 2011-10-12 at 17:51 -0700, Jeremy Fitzhardinge wrote:
>
> This is is all unnecessary complication if you're not using PV ticket
> locks, it also uses the jump-label machinery to use the standard
> "add"-based unlock in the non-PV case.
>
> if (TICKET_SLOWPATH_FLAG &&
> unlikely(static_branch(¶virt_ticketlocks_enabled))) {
> arch_spinlock_t prev;
>
> prev = *lock;
> add_smp(&lock->tickets.head, TICKET_LOCK_INC);
>
> /* add_smp() is a full mb() */
>
> if (unlikely(lock->tickets.tail & TICKET_SLOWPATH_FLAG))
> __ticket_unlock_slowpath(lock, prev);
> } else
> __add(&lock->tickets.head, TICKET_LOCK_INC,
> UNLOCK_LOCK_PREFIX);
Not that I mind the jump_label usage, but didn't paravirt have an
existing alternative() thingy to do things like this? Or is the
alternative() stuff not flexible enough to express this?
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
Home