Public bug reported:
I've got a set of benchmarks that use clock_gettime like:
clock_gettime(CLOCK_REALTIME, &tbefore);
for(l=0;l<numloops;l++) {
dostuff
}
clock_gettime(CLOCK_REALTIME, &tafter);
nsdiff=(double)(tafter.tv_nsec - tbefore.tv_nsec);
nsdiff+=1000000000.0 *(tafter.tv_sec - tbefore.tv_sec);
and I've just reinstalled our local panda to using Linaro 11.09 (kernel
3.0.0-1404-linaro-lt-omap)
and it's starting to get weird timing artifacts.
For example:
smarter_strlen_ldrd: ,102400, loops of ,62, bytes=6.054688 MB, transferred in
,3936768.000000 ns, giving, 1537.984331 MB/s
smarter_strlen_ldrd: ,102400, loops of ,32, bytes=3.125000 MB, transferred in
,0.000000 ns, giving, inf MB/s
smarter_strlen_ldrd: ,102400, loops of ,16, bytes=1.562500 MB, transferred in
,4180909.000000 ns, giving, 373.722557 MB/s
Now there is no way that loop took 0.000000 ns! Running the same binary
on an older installation runs fine.
Dave
** Affects: linux-linaro-omap (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/873453
Title:
odd timing behaviour on panda
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