Messages in this thread | | | Date | Wed, 17 Dec 2008 10:18:45 +0100 | From | Andi Kleen <> | Subject | Re: [Perfctr-devel] [patch] Performance Counters for Linux, v4 |
| |
> To make life easier for developers not interested in exact measuring, but in > cross-platform development, PAPI has introduced "generic" events. These are > documented not to be interpretable in a cross-platform manner - and > typically consist of aggregation of a number of low-level architecture > specific events. Instead a measure as PERF_COUNT_CACHE_REFERENCES tries to > create an event set that is a "best effort" for the platform. Typically it > would try to count read and write events to L1 and L2, but depending on the
The point was that L1 and L2/L3 behave so differently in practice due to their latency/bandwidth differences (typically L1 is more like a slower register file while L3 is more like faster DRAM) that it's unclear that any generic event not defining what it means is any useful.
I could see the point of generic FLC/LLC cache events perhaps, but not of a single one lumping these two together.
But although with multi core it looks like 3 level hierarchies are becoming more and more common and also more important to know about.
-Andi
-- ak@linux.intel.com
| |