* Alexandre Montplaisir ([email protected]) wrote: > On 10-08-17 03:54 PM, Mathieu Desnoyers wrote: [...] >> Oh, and by the way, given that these are arrays made of one variable per >> cpu, the extra space allocated will not consume extra cache lines in any >> of the CPU. We're just wasting a bit a memory here, not adding to cache >> pressure. >> >> Mathieu > > Sorry to chime in, but wouldn't padding to 128 bytes on architectures > with 64-byte cache lines "waste" an extra line every time, thus > indirectly adding to cache pressure?
A cache line is only used if the data located in that cache line is touched. If we only have padding in the second half of the 128 bytes, then the associated 64 bytes cache line is never fetched by the cpu. But reality can be a bit different when we speak of sequential accesses with prefetching. However, this apply well to randomly-accessed memory. Does that make sense ? Thanks, Mathieu > > (relatively newbie here, please be gentle :) ) > > Alexandre -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com _______________________________________________ ltt-dev mailing list [email protected] http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
