Messages in this thread | | | Date | Wed, 24 Oct 2012 17:11:00 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/2] percpu-rw-semaphores: use light/heavy barriers |
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On 10/23, Peter Zijlstra wrote: > > On Tue, 2012-10-23 at 21:23 +0200, Oleg Nesterov wrote: > > > > static void mb_ipi(void *arg) > > { > > smp_mb(); /* unneeded ? */ > > } > > > > static void force_mb_on_each_cpu(void) > > { > > smp_mb(); > > smp_call_function(mb_ipi, NULL, 1); > > } > > You know we're spending an awful lot of time and effort to get rid of > such things, right? RT and HPC people absolutely hate these random IPI > things.
No I do not know ;) but I am not suprized.
And,
> > I have to admit, I have > > no idea how much cli/sti is slower compared to preempt_disable/enable. > > > A lot.. esp on stupid hardware (insert pentium-4 reference), but I think > its more expensive for pretty much all hardware,
Thanks Peter, this alone answers my question.
Oleg.
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