Paul Allen wrote: > >From Michal Mertl <mime_at_traveller.cz>, Sun, Jul 30, 2006 at 01:50:36AM +0200: > > Michal Mertl wrote: > > > Paul Allen wrote: > > > > Surely all you need to do is a cheap crit_enter,crit_exit > > > > while updating the 64-bit per cpu counters. and on > > > > a 64-bit arch you skip the crit_enter,crit_exit. > > > > > > Critical_enter/exit seem to be quite lightweight (single > > > read/modify/write of a variable). > > > > One more question. Why do you say that crit_* can be avoided on 64-bit > > arch? If the reason was that "increment of a 64 bit number is one > > operation there" it probably is not true - as somebody already stated, > > some instruction sets don't allow atomic increment of a memory location. > > > > Michal > > Which FreeBSD tier-I 64b arch do you have in mind... I was referring to what Peter Jeremy said earlier in this thread: > RISC architectures usually only have TAS lock primitives (because "inc > mem" doesn't exist) and so require a spinlock to perform an atomic > update. I don't know anything that low level about any platform but i386. MichalReceived on Sun Jul 30 2006 - 07:07:50 UTC
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