|
From: Ashley P. <as...@qu...> - 2006-03-28 17:01:38
|
On Tue, 2006-03-28 at 17:45 +0100, Julian Seward wrote: > > r5774. memcheck is now in the same ballpark as --tool=none which it > > never has been before. > > Ashley - you mean when you do MPI bandwidth tests? It's MPI latency I've been looking at, natively it's ~2uSec, under valgrind with --tool=none it's about 35 uSec and until recently it's been ~800 uSec under memcheck. memcheck is now almost the same as none. > 'cos although > memcheck is much improved as a result of this, it's still nowhere > near as fast as 'none' for computation. For a MPI test though, > in which mostly you're waiting for the nic, all that V is really > doing is painting memory as it goes in/out, as per your ioctls > wrappers, and for this particular case - changing memory permissions - > Nick's work does indeed give a big speedup. The performance of the client checks will have had an effect here although as you say the code doesn't do much computation. Ashley, |