On 2012/1/19 23:23, John Baldwin wrote:
On Thursday, January 19, 2012 12:57:50 am David Xu wrote:
rdtsc() may not work on SMP, so I have updated it to use clock_gettime
to get total time.
http://people.freebsd.org/~davidxu/bench/semaphore2/
<http://people.freebsd.org/%7Edavidxu/bench/semaphore2/>
Still, lfence is a lot faster than atomic lock.
http://www.freebsd.org/~jhb/patches/amd64_fence.patch
This the patch I've had for quite a while. Can you retest with this? You'll
probably have to install the updated header in /usr/include as well.
The lines in atomic_load_acq() seem not what I want:
+ v = *p; \
+ __asm __volatile("lfence" ::: "memory"); \
I think they should be swapped ?
+ __asm __volatile("lfence" ::: "memory"); \
+ v = *p; \
What I need in the semaphore code is read can not pass write in such a special
case.
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