Thread: [perfmon2] Itanium Montecito Bus Utilization
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From: Vineeth M. <mek...@um...> - 2010-06-28 00:08:02
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Hi All, I am trying to measure bus utilization of some benchmarks on Itanium Montecito machine. I followed the procedure in http://www.ice.gelato.org/oct06/pres_pdf/gelato_ICE06oct_perfmon2_eranian_hp.pdf and measured the bus utilization. Now, I am not sure at what percentage of value is the bus saturated? Is it 100%? Say, if my bus utilization is 75%, can I say the bus is saturated? I will be grateful if someone can shed some light on this. Thanks, Vineeth |
From: Rick J. <ric...@hp...> - 2010-06-28 20:52:32
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Vineeth Mekkat wrote: > Hi All, > > I am trying to measure bus utilization of some benchmarks on Itanium > Montecito machine. I followed the procedure in > http://www.ice.gelato.org/oct06/pres_pdf/gelato_ICE06oct_perfmon2_eranian_hp.pdf > and measured the bus utilization. Now, I am not sure at what percentage > of value is the bus saturated? Is it 100%? What sort of system are you measuring? A single-bus system, or a "cell-based" system? > Say, if my bus utilization is 75%, can I say the bus is saturated? > > I will be grateful if someone can shed some light on this. I'm not sure how much light I will shed, but when it comes to memory busses, I've never been comfortable much past 80%. |
From: Vineeth M. <mek...@um...> - 2010-06-28 21:06:53
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Thanks Rick for the message. My machine is a HP server rx4640 ( http://h18000.www1.hp.com/products/quickspecs/11847_div/11847_div.HTML) with 4 montecito processors. I understand this is a single-bus system. I run up to 8 threads (of a maximum 16) so as not to 'invoke' hyperthreading. Then measure BUS_DATA_CYCLE_ANY to calculate bus utilization. My intention is to see if the benchmark is saturating the memory bus with off-chip accesses. Vineeth On 06/28/2010 03:52 PM, Rick Jones wrote: > Vineeth Mekkat wrote: >> Hi All, >> >> I am trying to measure bus utilization of some benchmarks on Itanium >> Montecito machine. I followed the procedure in >> http://www.ice.gelato.org/oct06/pres_pdf/gelato_ICE06oct_perfmon2_eranian_hp.pdf >> and measured the bus utilization. Now, I am not sure at what >> percentage of value is the bus saturated? Is it 100%? > > What sort of system are you measuring? A single-bus system, or a > "cell-based" system? > >> Say, if my bus utilization is 75%, can I say the bus is saturated? >> >> I will be grateful if someone can shed some light on this. > > I'm not sure how much light I will shed, but when it comes to memory > busses, I've never been comfortable much past 80%. |
From: Rick J. <ric...@hp...> - 2010-06-28 21:12:17
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Vineeth Mekkat wrote: > Thanks Rick for the message. > > My machine is a HP server rx4640 ( > http://h18000.www1.hp.com/products/quickspecs/11847_div/11847_div.HTML) > with 4 montecito processors. I understand this is a single-bus system. That is correct. > I run up to 8 threads (of a maximum 16) so as not to 'invoke' > hyperthreading. Then measure BUS_DATA_CYCLE_ANY to calculate bus > utilization. My intention is to see if the benchmark is saturating the > memory bus with off-chip accesses. While I am not willing to put a stake in the ground and say unequivocally "yes you are saturated" I wouldn't expect to be able to go much farther if you are at 75% utilization of that bus. I do not know how well "Linux" will "park" the second thread in each core - based on that, I would suggest running cpuconfig at EFI and explicitcly disabling HT. rick jones > > Vineeth > > On 06/28/2010 03:52 PM, Rick Jones wrote: > >> Vineeth Mekkat wrote: >> >>> Hi All, >>> >>> I am trying to measure bus utilization of some benchmarks on Itanium >>> Montecito machine. I followed the procedure in >>> http://www.ice.gelato.org/oct06/pres_pdf/gelato_ICE06oct_perfmon2_eranian_hp.pdf >>> and measured the bus utilization. Now, I am not sure at what >>> percentage of value is the bus saturated? Is it 100%? >> >> >> What sort of system are you measuring? A single-bus system, or a >> "cell-based" system? >> >>> Say, if my bus utilization is 75%, can I say the bus is saturated? >>> >>> I will be grateful if someone can shed some light on this. >> >> >> I'm not sure how much light I will shed, but when it comes to memory >> busses, I've never been comfortable much past 80%. > |