Re: [Gems-users] Low IPC in Opal

["Daniel Sánchez Pedreño" <sanatox@xxxxxxxxx>]

Dan,

in order to discard memory as the cause of the low IPC I have configured the latencies to 1 cycle for hits or misses for all acceses. Still, the IPC continues extremely low.

There are a few things in the code which I have changed to increase performance:

• RETIREMENT_CACHE_ACCESS = 0. If this flag is activated, any memory access performs two different requests to Ruby (with the addittional overhead).
• In pseq.C, in function postEvent, I have changed "cyclesInFuture - 1" by just "cyclesInFuture". If not, events are not woken up correctly. For example, if you want an instruction to be woken-up in 1 cycle, with the previous parameters, it will be woken 8 cycles later. This is curiously the time indicated by the variable EVENT_QUEUE_SIZE in scheduler.h

With these changes I get an IPC around 0.88 for FFT in 1 processor.

Has anybody experiment with Opal an SPLASH-2? If this IPC something usual? Could anybody point me some others benchmarks to obtaing a higher IPC?.
Maybe I am doing something wrong. Could anybody send me a correct configuration file for Opal and Ruby?.

Thanks

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