Messages in this thread | | | Subject | Re: [PATCH 1/5] ftrace: Synchronize variable setting with breakpoints | From | Peter Zijlstra <> | Date | Thu, 31 May 2012 22:40:57 +0200 |
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On Thu, 2012-05-31 at 16:37 -0400, Steven Rostedt wrote: > On Thu, 2012-05-31 at 22:26 +0200, Peter Zijlstra wrote: > > > Right, but when you loose stop-machine you could simply do 30k > > kmap_atomic/kunmap_atomic's consecutively since you're not holding > > anybody up. > > It requires 3 IPIs per update too. Thus that's 90,000 IPIs you are > blasting^Wsending to all CPUs.
Uhm, no.
for_each() { kmap_atomic() frob int3 kunmap_atomic(); }
sync-ipi-broadcast();
for_each() { kmap_atomic(); frob tail kunmap_atomic(); }
sync-ipi-broadcast();
for_each() { kmap_atomic(); frob head kunmap_atomic(); };
sync-ipi-broadcast();
How is that sending 90k ipis?
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