On Tue, Jun 18, 2013 at 02:51:13PM +0930, Rusty Russell wrote:
> Tejun Heo writes:
> > Buth yeah, interesting trick. We'll be doing IPIs, flushing TLB and
> > taking faults until it hits zero. It'll all depend on the frequency
> > of preemption but given that branches don't tend to be too expens
Tejun Heo writes:
> Buth yeah, interesting trick. We'll be doing IPIs, flushing TLB and
> taking faults until it hits zero. It'll all depend on the frequency
> of preemption but given that branches don't tend to be too expensive
> on modern processors, maybe it'd be a bit too hairy for possibly
Hello, Rusty.
On Sun, Jun 16, 2013 at 04:16:15PM +0930, Rusty Russell wrote:
> > For most use cases, the trade-off should be fine. With any kind of
> > cross-cpu traffic, which there usually will be, it should be an easy
> > win for the percpu-refcount even when CONFIG_PREEMPT; however, I've
> >
Tejun Heo writes:
> I've been running some performance tests with different preemption
> levels and, with CONFIG_PREEMPT, the percpu ref could be slower by
> around 10% or at the worst contrived case maybe even close to 20% when
> compared to simple atomic_t on a single CPU (when hit by multiple C
Hello, Paul.
On Sun, Jun 16, 2013 at 07:13:35AM -0700, Paul E. McKenney wrote:
> CONFIG_TREE_PREEMPT_RCU does have an increment, decrement (sort of),
> and check in its rcu_read_lock() and rcu_read_unlock(), which will
> add overhead that might well be noticeable compared to CONFIG_TREE_RCU's
> ze
On Sat, Jun 15, 2013 at 07:36:11PM -0700, Tejun Heo wrote:
> Hello, guys.
>
> Kent recently implemented a generic percpu reference counter. It's
> scheduled to be merged in the coming merge window and some part of
> cgroup refcnting is already converted to it.
>
>
> https://git.kernel.org/cgit
Hello, guys.
Kent recently implemented a generic percpu reference counter. It's
scheduled to be merged in the coming merge window and some part of
cgroup refcnting is already converted to it.
https://git.kernel.org/cgit/linux/kernel/git/tj/percpu.git/tree/include/linux/percpu-refcount.h?h=for-
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