On 11 Jul 2010, at 04:18, Gabor PALI wrote: > On Sat, Jul 10, 2010 at 5:24 PM, Robert N. M. Watson > <rwat...@freebsd.org> wrote: >> If we can do it in one atomic in the common case, and two atomics in an edge >> case, that sounds fine. I think any use of locking(9) would be sufficiently >> costly as to not be worth the improvements in consistency, given the >> frequency of statistics operations. > > I have tried to use atomic operations for counting (without > locking(9)), but they turned out to be significantly slower than the > naive case indeed. If consistency is not so important for statistics, > whether would it be safe to simply use 64-bit variables for counters > everywhere on all architectures?
I think the worry comes down to: an occasional missed packet is OK, but a duplicated carry(for example) from the lower 32 bits to the upper 32 bits would put the counter off by 4 billion, which is not really acceptable. What sort of measurement did you do to show the speed loss, BTW? Robert _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
