hwpmc overflow

Anton Yuzhaninov citrin at citrin.ru
Tue Sep 20 20:27:30 UTC 2011


On Tue, 20 Sep 2011 16:12:57 +0000 (UTC), Anton Yuzhaninov wrote:
AY> pmcstat -C -w1 -d -p
AY> INSTR_RETIRED_ANY -p DTLB_MISSES.ANY -p MEM_LOAD_RETIRED.DTLB_MISS -p
AY> ITLB_MISSES.ANY -p MEM_LOAD_RETIRED.L3_MISS
AY> 
AY> With -C values should monotonous increase, but in output I see
AY> overflous.
AY> 
AY> Example output:
AY> http://pastebin.com/JiEF9AcU
AY> 
AY> 2120463169
AY> 2139646836
AY> 281472837488169
AY> 281472855479093
AY> 
AY> 2139646836 is near to 2^31 - max value for signed int (int32_t)
AY> 

Some more debug info:
# uname -a
FreeBSD test.vega.ru 8.2-STABLE FreeBSD 8.2-STABLE #0: Tue Sep 20 14:41:45 UTC 2011     root at example.ru:/usr/obj/usr/src/sys/GENERIC  amd64

hwpmc: TSC/1/64/0x20<REA> IAP/4/48/0x3ff<INT,USR,SYS,EDG,THR,REA,WRI,INV,QUA,PRC> IAF/3/48/0x61<INT,REA,WRI> UCP/8/48/0x3f8<EDG,THR,REA,WRI,INV,QUA,PRC> UCF/1/48/0x60<REA,WRI>

kern.hwpmc.debugflags: pmc=ops

When in pmc out shown values
2111155514
281473102541203

in dmesg I can see
PMC:OPS:2: rw id=4 -> old 7dd5ad3
PMC:OPS:2: rw id=4 -> old ffff904a7193

So probmles somewhere in kernel (not in pmcstat)

-- 
 Anton Yuzhaninov



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