Discussion:
HPCs for DRAM
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Dimitris Ganosis
2016-06-18 12:29:17 UTC
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I run an Intel(R) Xeon(R) CPU E5520 @ 2.27GHz and follow, apart from perf
list, this list
<http://oprofile.sourceforge.net/docs/intel-corei7-events.php>for the
available counters.
Based on Linux perf events Event Sources
<http://www.brendangregg.com/perf.html> I expected that counters like

MEM_STORE_RETIRED and MEM_LOAD_RETIRED

would capture only DRAM's activity. I mean that if I don't use DRAM it's
bizarre to me to see these counters have the same trend with CPI and other
cpu counters. I run a cpu intensive benchmark which does not use DRAM, as I
could see from htop, and these two counters followed the same trend, in the
graph that I created later, with almost all the other counters. So, my
question is if there are any counters which are "triggered" only when I use
DRAM?
Like the IO_TRANSACTIONS which is triggered only when I have I/Os.
Thank you!
Dimitris Ganosis
2016-06-18 13:01:25 UTC
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PS. The ideal would be to distinguish memory bandwidth and memory capacity
like MEMORY_BW_READS
<https://yunmingzhang.wordpress.com/2015/07/22/measure-memory-bandwidth-using-uncore-counters/>
but it's not available, at least with this name, in my machine.
Post by Dimitris Ganosis
list, this list
<http://oprofile.sourceforge.net/docs/intel-corei7-events.php>for the
available counters.
Based on Linux perf events Event Sources
<http://www.brendangregg.com/perf.html> I expected that counters like
MEM_STORE_RETIRED and MEM_LOAD_RETIRED
would capture only DRAM's activity. I mean that if I don't use DRAM it's
bizarre to me to see these counters have the same trend with CPI and other
cpu counters. I run a cpu intensive benchmark which does not use DRAM, as I
could see from htop, and these two counters followed the same trend, in the
graph that I created later, with almost all the other counters. So, my
question is if there are any counters which are "triggered" only when I use
DRAM?
Like the IO_TRANSACTIONS which is triggered only when I have I/Os.
Thank you!
Michael Petlan
2016-06-20 15:45:25 UTC
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Hi Dimitris,
Post by Dimitris Ganosis
PS. The ideal would be to distinguish memory bandwidth and memory capacity
like MEMORY_BW_READS
<https://yunmingzhang.wordpress.com/2015/07/22/measure-memory-bandwidth-using-uncore-counters/>
but it's not available, at least with this name, in my machine.
The attached program should detect whether your CPU supports MBM or not.
However, if it is a Nehalem (model = 26, 30 or 46) or similar, it does
not for sure.
What are the family number and model number (lscpu, cat /proc/cpuinfo, ...)?
Post by Dimitris Ganosis
Post by Dimitris Ganosis
list, this list
<http://oprofile.sourceforge.net/docs/intel-corei7-events.php>for the
available counters.
Based on Linux perf events Event Sources
<http://www.brendangregg.com/perf.html> I expected that counters like
MEM_STORE_RETIRED and MEM_LOAD_RETIRED
would capture only DRAM's activity. I mean that if I don't use DRAM it's
bizarre to me to see these counters have the same trend with CPI and other
cpu counters. I run a cpu intensive benchmark which does not use DRAM, as I
could see from htop, and these two counters followed the same trend, in the
graph that I created later, with almost all the other counters. So, my
question is if there are any counters which are "triggered" only when I use
DRAM?
Like the IO_TRANSACTIONS which is triggered only when I have I/Os.
Thank you!
Could you provide more details? How could I reproduce that?
Michael

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