Messages in this thread | | | Date | Wed, 1 Jul 2015 09:17:05 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC tip/core/rcu 0/5] Expedited grace periods encouraging normal ones |
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On Wed, Jul 01, 2015 at 04:17:10PM +0200, Peter Zijlstra wrote: > On Wed, Jul 01, 2015 at 07:00:31AM -0700, Paul E. McKenney wrote: > > > That is a bit extreme, Peter. > > Of course; but I'm really not seeing people taking due care with them
;-)
> > Are a huge pile of them coming in this merge window or something? > > What raised your concerns on this issue? > > This is complete horse manure (breaking the nvidiot binary blob is a > good thing): > > 74b51ee152b6 ("ACPI / osl: speedup grace period in acpi_os_map_cleanup")
Really???
I am not concerned about this one. After all, one of the first things that people do for OS-jitter-sensitive workloads is to get rid of binary blobs. And any runtime use of ACPI as well. And let's face it, if your latency-sensitive workload is using either binary blobs or ACPI, you have already completely lost. Therefore, an additional expedited grace period cannot possibly cause you to lose any more.
> Also, I'm not entirely convinced things like: > > fd2ed4d25270 ("dm: add statistics support") > 83d5e5b0af90 ("dm: optimize use SRCU and RCU") > ef3230880abd ("backing-dev: use synchronize_rcu_expedited instead of synchronize_rcu") > > Are in the 'never' happens category. Esp. the backing-dev one, it > triggers every time you unplug a USB stick or similar.
Which people should be assiduously avoiding for any sort of industrial-control system, especially given things like STUXNET.
> Rejigging a DM might indeed be rare enough; but then again, people use > DM explicitly so they can rejig while in operation.
They rejig DM when running OS-jitter-sensitive workloads?
> Also, they really do not explain how expedited really is the only option > available. Why things can't be batched etc..
Fair question!
Thanx, Paul
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