diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2015-09-04 17:25:23 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-10-22 14:49:15 -0700 |
| commit | 304b8b47da42152baf13fbf73f074db76d970bc9 (patch) | |
| tree | 1a70788ee18ef393f190da86c7c8b5dc5df0a8e4 /include | |
| parent | d78a2be4f9a1b9a31dff96e17d175860c30db4c2 (diff) | |
| download | lwn-304b8b47da42152baf13fbf73f074db76d970bc9.tar.gz lwn-304b8b47da42152baf13fbf73f074db76d970bc9.zip | |
locking/qspinlock/x86: Fix performance regression under unaccelerated VMs
commit 43b3f02899f74ae9914a39547cc5492156f0027a upstream.
Dave ran into horrible performance on a VM without PARAVIRT_SPINLOCKS
set and Linus noted that the test-and-set implementation was retarded.
One should spin on the variable with a load, not a RMW.
While there, remove 'queued' from the name, as the lock isn't queued
at all, but a simple test-and-set.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Dave Chinner <david@fromorbit.com>
Tested-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/20150904152523.GR18673@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-generic/qspinlock.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index 83bfb87f5bf1..e2aadbc7151f 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -111,8 +111,8 @@ static inline void queued_spin_unlock_wait(struct qspinlock *lock) cpu_relax(); } -#ifndef virt_queued_spin_lock -static __always_inline bool virt_queued_spin_lock(struct qspinlock *lock) +#ifndef virt_spin_lock +static __always_inline bool virt_spin_lock(struct qspinlock *lock) { return false; } |