Hi Andreas, Thanks for the details. But the same workload gives significant increase in average memory access time if i run gem5 with integrated dramsim2 and increase only tRCD and tRP. As you said, both tRCD and tRP are associated with opening and closing of row. The results of dramsim2 and gem5 DDR3 memory model suggests that gem5 keeps the rows open for much longer duration which causes significantly higher pageHitRate.
Regards, On 2 June 2014 10:36, Andreas Hansson <[email protected]> wrote: > Hi Ahmad, > > Increasing tRCD and tRP will essentially make it more costly to open and > close a page. If you have good page hit-rate, and good distribution over > the banks, then the effects of the increased timings can be hidden (at > least from the perspective of the average latency). When you increase tCL > you are delaying every single access. > > bytesPerActivate is a histogram statistic associated with the DRAM > controller. You should find it in the stats.txt along with all the other > stats. > > Andreas > > From: Ahmad Hassan via gem5-users <[email protected]> > Reply-To: Ahmad Hassan <[email protected]>, gem5 users mailing list < > [email protected]> > Date: Monday, 2 June 2014 10:29 > To: gem5 users mailing list <[email protected]> > Subject: [gem5-users] DDR timing model > > Hi Andreas, > > [Moving discussion from http://reviews.gem5.org/r/2109] > > If I only increase the tCL parameter from 13.75ns to 61ns [4.4x times > default DDR3), then I notice 3.2x times increase in avgMemAccLat. This is > what we should expect. Can we use tCL to simulate slow DDR3? My > understanding is that, we cannot do that because tCL represents column > address strobe and it affects bandwidth. > > But I cannot produce the same result by changing tRCD = '61ns', tRP = > '165ns'. tRCD affects read latency and tRP affects write latency. I only > get an increase in avgMemAccLat by 1.2x times default DDR3. > > Results: > > For default DDR3: > avgMemAccLat 22133.24 > totMemAccLat 12166996811 > > For tRCD = '61ns', tRP = '165ns'. > avgMemAccLat 27473.08 > totMemAccLat 15104591550 > > For tCL = '61ns' > avgMemAccLat 71630.94 > totMemAccLat 39376746052 > > I did not find any 'bytesPerActive' attribute in stats file. Where shall > I see this? > > Thanks. > > > > > > -- IMPORTANT NOTICE: The contents of this email and any attachments are > confidential and may also be privileged. If you are not the intended > recipient, please notify the sender immediately and do not disclose the > contents to any other person, use it for any purpose, or store or copy the > information in any medium. Thank you. > > ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, > Registered in England & Wales, Company No: 2557590 > ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, > Registered in England & Wales, Company No: 2548782 >
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