Messages in this thread |  | | Date | Tue, 25 Feb 2014 20:32:38 -0700 | From | Jeff Law <> | Subject | Re: [RFC][PATCH 0/5] arch: atomic rework |
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On 02/25/14 17:15, Paul E. McKenney wrote: >> I have for the last several years been 100% convinced that the Intel >> memory ordering is the right thing, and that people who like weak >> memory ordering are wrong and should try to avoid reproducing if at >> all possible. But given that we have memory orderings like power and >> ARM, I don't actually see a sane way to get a good strong ordering. >> You can teach compilers about cases like the above when they actually >> see all the code and they could poison the value chain etc. But it >> would be fairly painful, and once you cross object files (or even just >> functions in the same compilation unit, for that matter), it goes from >> painful to just "ridiculously not worth it". > > And I have indeed seen a post or two from you favoring stronger memory > ordering over the past few years. ;-) I couldn't agree more.
> > Are ARM and Power really the bad boys here? Or are they instead playing > the role of the canary in the coal mine? That's a question I've been struggling with recently as well. I suspect they (arm, power) are going to be the outliers rather than the canary. While the weaker model may give them some advantages WRT scalability, I don't think it'll ultimately be enough to overcome the difficulty in writing correct low level code for them.
Regardless, they're here and we have to deal with them.
Jeff
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