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authorJeremy Fitzhardinge <jeremy@goop.org>2008-07-07 12:07:51 -0700
committerIngo Molnar <mingo@elte.hu>2008-07-16 11:15:53 +0200
commit8efcbab674de2bee45a2e4cdf97de16b8e609ac8 (patch)
tree1b45a9446e471bfdba21e7982c87aef47d2f8313 /arch
parent74d4affde8feb8d5bdebf7fba8e90e4eae3b7b1d (diff)
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paravirt: introduce a "lock-byte" spinlock implementation
Implement a version of the old spinlock algorithm, in which everyone spins waiting for a lock byte. In order to be compatible with the ticket-lock's use of a zero initializer, this uses the convention of '0' for unlocked and '1' for locked. This algorithm is much better than ticket locks in a virtual envionment, because it doesn't interact badly with the vcpu scheduler. If there are multiple vcpus spinning on a lock and the lock is released, the next vcpu to be scheduled will take the lock, rather than cycling around until the next ticketed vcpu gets it. To use this, you must call paravirt_use_bytelocks() very early, before any spinlocks have been taken. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Christoph Lameter <clameter@linux-foundation.org> Cc: Petr Tesarik <ptesarik@suse.cz> Cc: Virtualization <virtualization@lists.linux-foundation.org> Cc: Xen devel <xen-devel@lists.xensource.com> Cc: Thomas Friebel <thomas.friebel@amd.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/paravirt.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index f3381686870..bba4041bb7f 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -268,6 +268,15 @@ enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
return __get_cpu_var(paravirt_lazy_mode);
}
+void __init paravirt_use_bytelocks(void)
+{
+ pv_lock_ops.spin_is_locked = __byte_spin_is_locked;
+ pv_lock_ops.spin_is_contended = __byte_spin_is_contended;
+ pv_lock_ops.spin_lock = __byte_spin_lock;
+ pv_lock_ops.spin_trylock = __byte_spin_trylock;
+ pv_lock_ops.spin_unlock = __byte_spin_unlock;
+}
+
struct pv_info pv_info = {
.name = "bare hardware",
.paravirt_enabled = 0,