On Sun, Dec 14, 2014 at 02:44:08AM +0100, Samuel Thibault wrote: > Does anybody with a bit of background with spl (I guess Richard?) see > any red flag here?
No, and in fact, I don't like the idea of SPL/IPL. For example, Linux doesn't care about them and merely disables or enables interrupts at the processor level, the semantics being all or nothing, and it shows it works quite well. An IPL (interrupt priority level) is basically a system of not-so-coarsed-grained locking. The spl (set priority level) functions act as lock/unlock primitives. In that regard, using cli/sti is equivalent to acquiring/releasing a big kernel lock. If the critical sections protected by this lock are all small enough, granularity tends to matter much less. My point being that this could be generalized for all IPLs, since they are all affected by the virtualization penalty. -- Richard Braun
