On 2013-01-31 10:33 AM, Till Schneidereit wrote:
In the long run, 1 and 3 are the same. If we know we're going to turn
it off, why not bite the bullet and do it now?
Because we're still missing plenty of optimizations in our code
to be fast in microbenchmarks. It would be quite huge pr loss if we suddenly
were 10-20% slower in benchmarks.
But we're getting better (that last spike is because bz managed to
effectively optimize out one test).
http://graphs.mozilla.org/graph.html#tests=[[73,1,1]]&sel=none&displayrange=365&datatype=running
Do we think the planned optimizations cause the gains through PGO to
be less pronounced? If not, then slowdown in benchmarks and associated
PR loss would be the same whenever we finally pulled the plug on PGO,
right?
I'm not sure what you mean. If we get 10% slower in Dromaeo by
disabling PGO and take a patch which makes us 20% faster regardless of
PGO, then we should expect an approximate 10% win as a result. But
generally, the game of trying to beat the compiler in its optimizations
is futile, since they can outsmart most programmers on their worst day. :-)
Ehsan
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