Ulrich.Windl@rz.uni-regensburg.de said:
Hi!
I think a problem with your test program is that you don't wait for the write() thread to finish before you try to read the mmap(). See how locking on a producer-consumer (or reader-writer) relationship is usually implemented (If you don't have it ready, I could send you the algorithms).
That shoudln't matter. The write thread opens the file descriptor with O_DSYNC, and all the test program is trying to verify is that the mmap eventually becomes consistent. You can ignore the pthread_barrier stuff, that just tries to eliminate thread creation time from the equation.
Now that I think about the output, there is a fairly obvious explanation for the numbers - 1 means the writer thread got scheduled first. However I'm still not sure why the # of iterations on MIPS is so high - scheduling resolution on the box maybe?
Martin