On 11/30/2011 09:44 AM, David Miller wrote: > Linux originally did RMO but I killed that several years ago, no > new chips are implementing RMO and this means all the necessary > membar instructions are nothing but pure overhead.
Well, you've now got the option for -mmemory-model=sc to omit every last one. > Solaris always ran userspace in TSO as far as I remember. Ok. > Your change will leave FreeBSD and NetBSD with the RMO setting, and > both of them run userland in TSO as well. Eh. It'll be easy enough for a bsd maintainer to update if they like. > BTW, Linux has a "memory_ordering" system call where you can change > the PSTATE_MM setting to whatever memory model you like. I suppose > Solaris has something similar. Interesting, but... > So one thing to consider doing is, if there is some doubt, to set > it explicitly to TSO in some crt code. ... easier to keep the RMO/PSO default in that case. r~
