Messages in this thread Patch in this message |  | | | Date | Thu, 8 May 2008 08:43:40 +0200 | | From | Ingo Molnar <> | | Subject | Re: AIM7 40% regression with 2.6.26-rc1 | |
* Zhang, Yanmin <yanmin_zhang@linux.intel.com> wrote:
> > Here's a trial balloon patch to do that.
> >
> > Yanmin - this is not well tested, but the code is fairly obvious,
> > and it would be interesting to hear if this fixes the performance
> > regression. Because if it doesn't, then it's not the BKL, or
> > something totally different is going on.
>
> Congratulations! The patch really fixes the regression completely!
> vmstat showed cpu idle is 0%, just like 2.6.25's.
great! Yanmin, could you please also check the other patch i sent (also
attached below), does it solve the regression similarly?
Ingo
---
lib/kernel_lock.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
Index: linux/lib/kernel_lock.c
===================================================================
--- linux.orig/lib/kernel_lock.c
+++ linux/lib/kernel_lock.c
@@ -46,7 +46,8 @@ int __lockfunc __reacquire_kernel_lock(v
task->lock_depth = -1;
preempt_enable_no_resched();
- down(&kernel_sem);
+ while (down_trylock(&kernel_sem))
+ cpu_relax();
preempt_disable();
task->lock_depth = saved_lock_depth;
@@ -67,11 +68,13 @@ void __lockfunc lock_kernel(void)
struct task_struct *task = current;
int depth = task->lock_depth + 1;
- if (likely(!depth))
+ if (likely(!depth)) {
/*
* No recursion worries - we set up lock_depth _after_
*/
- down(&kernel_sem);
+ while (down_trylock(&kernel_sem))
+ cpu_relax();
+ }
task->lock_depth = depth;
}
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