On Fri, Aug 02, 2013 at 01:53:22AM +0530, Raghavendra K T wrote:
You need to learn to trim your replies.. I already stopped reading that
paravirt thread because of it. Soon I'll introduce you to my /dev/null
mail reader.
> On 08/01/2013 08:07 AM, Waiman Long wrote:
> >+static __always_inline void queue_spin_lock(struct qspinlock *lock)
> >+{
> >+ if (likely(queue_spin_trylock(lock)))
> >+ return;
> >+ queue_spin_lock_slowpath(lock);
> >+}
>
> quickly falling into slowpath may hurt performance in some cases. no?
>
> Instead, I tried something like this:
>
> #define SPIN_THRESHOLD 64
>
> static __always_inline void queue_spin_lock(struct qspinlock *lock)
> {
> unsigned count = SPIN_THRESHOLD;
> do {
> if (likely(queue_spin_trylock(lock)))
> return;
> cpu_relax();
> } while (count--);
> queue_spin_lock_slowpath(lock);
> }
>
> Though I could see some gains in overcommit, but it hurted undercommit
> in some workloads :(.
This would break the FIFO nature of the lock.
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