Hi,
One of the functions in smpl_pebs.c is "process_smpl_buf " . It has a check
condition (modified slightly for running with multiple threads) as follows :
if (hdr->hdr_overflows <= last_overflow[id] && last_overflow[id] != ~0)
{
warning("skipping identical set of samples %"PRIu64" <= %"PRIu64"\n",
hdr->hdr_overflows, last_overflow);
return;
}
/*In my case this condition gets executed individually for each thread -
last_overflow[id] is an array for thread with thread # id, argument hdr is
passed in the function and is unique for each thread */
Here, hdr->hdr_overflows should be monotonically increasing (across
multiple function invocations) for each thread. But somewhere in the
middle, I notice a spike in its value (described below).
Because of it , all the following invocations of this function just return
without counting samples. Now, I can hack it pretty easily by just
updating the last_overflow[id] to the current hdr->hdr_overflows (treating
that one value as unexpected). But I would like to understand the reason
for this. Is this a bug in perfmon ?
I am using perfmon patched 2.6.17 kernel.
Following header overflows((hdr->hdr_overflows) have been tracked only for
thread 0. And the test program was run for 2 threads.
Header overflow = 1781
Header overflow = 1782
Header overflow = 1783
Header overflow = 1784
Header overflow = 1785
Header overflow = 1786
Header overflow = 1787
Header overflow = 1788
Header overflow = 1789
<<<<<<<<<<<<<<<<< Header overflow = 2947 >>>>>>>>>>>>>>>>>>>>>>>>>>
Header overflow = 1790
Header overflow = 1791
Header overflow = 1792
Header overflow = 1793
Header overflow = 1794
Header overflow = 1795
Header overflow = 1796
Header overflow = 1797
Header overflow = 1798
Header overflow = 1799
Header overflow = 1800
--
Regards,
Vivek Thakkar
Regards,
Vivek
---------------------
MS, CSC Department
NC State University
2834 Avent Ferry Road, Apt. 202
Raleigh, NC, 27606
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