On 3/3/2011 1:45 PM, David Miller wrote: >> I'm finding it hard to understand how the Sparc code handles icache >> coherence. It seems that the Spitfire MMU is the interesting one, but the >> hard case seems to be when a process migrates around to various cores >> during execution (thus leaving incoherent icache lines everywhere), and the >> page is then freed and re-used for different executable code. I'd think >> that there would have to be xcall IPIs to flush all the cpus' icaches, or >> to flush every core in the cpu_vm_mask plus do something at context switch, >> but I don't see any of that. No doubt I'm missing something :-) > flush_dcache_page() remembers the cpu that wrote to the page (in the > page flags), and cross-calls to that specific cpu. > > It is only that cpu which must flush his I-cache, since all other cpus > saw the write on the bus and updated their I-cache lines as a result. > > See, in the sparc64 case, the incoherency issue is purely local to the > store. The problem case is specifically the local I-cache not seeing > local writes, everything else is fine. CPU I-caches see writes done > by other cpus, just not those done by the local cpu. Thanks, that makes sense. Our architecture has no bus to snoop, so we couldn't take advantage of that approach. -- Chris Metcalf, Tilera Corp. http://www.tilera.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>