In single core case, there is a 1 MB L2 cache. In 4-core case, each core has its own private L2 cache of size 1 MB. As they are not shared, i dont understand the reason for different cache miss rates.
Best, Fulya Kaplan > On Nov 4, 2013, at 7:55 PM, "Tao Zhang" <[email protected]> wrote: > > Hi Fulya, > > What’s the L2 cache size of the 1-core test? Is it equal to the total > capacity of 4-core case? The stats indicates that 4-core test has less L2 > cache miss rate, which may be the reason of IPC improvement. > > -Tao > > From: [email protected] [mailto:[email protected]] On > Behalf Of Fulya Kaplan > Sent: Monday, November 04, 2013 10:20 AM > To: gem5 users mailing list > Subject: [gem5-users] Weird IPC statistics for Spec2006 Multiprogram mode > > Hi all, > I am running Spec 2006 on X86 with the version gem5-stable-07352f119e48. I am > using multiprogram mode with syscall emulation. I am trying to compare the > IPC statistics for 2 cases: > 1)Running benchmark A on a single core > 2)Running 4 instances of benchmark A on a 4-core system with 1MB private L2 > cashes. > All parameters are the same for the 2 runs except the number of cores. > I am expecting some IPC decrease for the 4-core case as the cores will share > the same system bus. However, for CactusADM and Soplex benchmarks, I see > higher IPC for case2 compared to case 1. > I look at the same phase of execution for both runs. I fastforward for 2 > billion instructions and grab the ipc for each of the cores corresponding to > the next 100 million instructions in detailed mode. > I ll report some other statistics for CactusADM to give a better idea of what > is going on. > Case 1: ipc=0.664141, L2_overall _accesses=573746, L2_miss_rate=0.616 > Case 2: cpu0_ipc=0.718562, cpu1_ipc= 0.720464, cpu2_ipc=0.717405, cpu3_ipc= > 0.716513 > L2_0_accesses=591607, L2_1_accesses=581846, L2_2_accesses=568095, > L2_3_accesses=561180, L2_0_missrate=0.452978, L2_1_missrate=0.454510, > L2_2_missrate=0.475646, L2_3_missrate=0.488171 > > Case 1:Running Time for 100M insts = 0.0716 sec > Case 2:Running Time for 100M insts = 0.066273 sec > > Do you have any idea what could be the problem? Actually, is this a problem > or something expected for some benchmarks? > Best, > Fulya Kaplan > > > > > > _______________________________________________ > gem5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users
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