Messages in this thread | | | Date | Fri, 20 Feb 2015 09:45:39 -0800 | From | Arjan van de Ven <> | Subject | Re: [PATCH tip/core/rcu 0/4] Programmatic nestable expedited grace periods |
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On 2/20/2015 9:43 AM, Peter Zijlstra wrote: > On Fri, Feb 20, 2015 at 09:32:39AM -0800, Arjan van de Ven wrote: >> there's a few others as well that I'm chasing down... >> .. but the flip side, prior to running ring 3 code, why NOT do fast expedites? > > So my objections are twofold: > > - I object to fast expedites in principle; they spray IPIs across the > system, so ideally we'd not have them at all, therefore also not at > boot. > > Because as soon as the option exists, people will use it for other > things too.
the option exists today in sysfs and kernel parameter... > > And esp. in bootup code you can special case a lot of stuff; there's > limited concurrency esp. because userspace it not there yet. So we might > not actually need those sync calls.
yeah I am going down that angle as well absolutely. but there are cases that may well be legit (or are 5 function calls deep into common code)
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