On Thu, 2014-01-16 at 11:51 -0800, Michael Dalton wrote: > On Thu, Jan 16, 2014 Ben Hutchings <bhutchi...@solarflare.com> wrote: > > It's simpler but we don't know if it's faster (and I don't believe that > > matters for the current usage). > > > > If one of these functions starts to be used in the data path, at that > > point it could be worth optimising, e.g. by doing a test for queue 0 and > > only then doing the pointer arithmetic with its implicit division. > Good catch, my statement above is incorrect. We don't know if this change > is a performance win, and it does introduce an implicit div. I agree this > function is not currently performance critical and is used only by for > reporting values to sysfs.
gcc usually do not emit a divide instruction to perform a divide by a constant, but uses a reciprocal operation (basically a multiply and a shift) So I am pretty sure this is faster than the loop. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
