you are missing the reason. read the paper.

brucee


On 22 September 2013 12:55, erik quanstrom <quanstro@quanstro.net> wrote:

> when i measure chan send performance with the attached program with
> the semaphore locks that have been made the default for sources and
> with the old locks, the old locks surprisingly outperform the new ones
> by a large margin.
>
> the test is let O be the number of buffers in the channel, and M be
> the number of sending procs, then cycles is the number of machine
> cycles required to send 1<<21 messages per proc, and receive them
> on a single listener.
>
> on my machine, i get the following raw numbers (averaged over a few tries):
>
>         new     1.84e9 cycles   O=10    M=1
>         old     1.10e9
>
>         new     4.61e9          O=0     M=1
>         old     4.38e9
>
>         new     1.55e10         O=10    M=8
>         old     2.74e10
>
>         new     3.64e10         O=0     M=8
>         old     5.14e10
>
> am i doing something fundamental wrong, or are the new locks substantially
> slower than the old ones?
>
> - erik