Hi, avadh, Thanks for your reply.
Another problem I found about the mesi cache in marss is when I run multiple program on multicore, I think it should not have any snoop hit (this function is called " handle_snoop_hit "in line 505 in mesiCache.cpp), since this is multiple program running on multi core which is not multithread, so there should not be snoop hit between different cores. But when I debug it, I found marss do call this handle_snoop_hit function frequently, do you have any idea about this? Thank you. Best zhe On Tue, Jun 14, 2011 at 11:14 AM, avadh patel <[email protected]> wrote: > > > On Tue, Jun 14, 2011 at 9:04 AM, Zhe Wang <[email protected]> wrote: > >> Hi, >> >> I have a question about the implementation of the mesi cache in marss. It >> seems marss does not copy back the modified version of cacheline into the >> shared last level cache in cache coherence. >> >> For example, in a four core processor, the L1 cache is private cache. L2 >> cache is the shared last level cache. >> If the L1 cache related to core1 has a read miss, and the L1 cache related >> to core3 has a modified copy of that cacheline. Then the L1 cache related to >> core3 should put the copy value on the bus and change the cacheline into >> Share state, these action could be find in line 558-562 in file >> /ptlsim/cache/cache/mesiCache.cpp file, Then this Modified value should be >> copied back to the Last Level Cache, I did not find any code in marss do >> this part. If this part miss, the value in last level cache and in the main >> memory is not consistent with the value in L1 cache, since the state of the >> requested cacheline in the L1 cache has been changed to share, so it will >> not be written back to last level cache and main memory. Does anyone has >> idea about this? Is this a bug of mesi cache in marss or there are >> something wrong with my understanding? Thanks >> >> This is a bug. Lower level cache has to be updated with latest copy. If > you have the patch send it to me, i'll update the repo. > > Thanks, > Avadh > > >> >> zhe >> >> _______________________________________________ >> http://www.marss86.org >> Marss86-Devel mailing list >> [email protected] >> https://www.cs.binghamton.edu/mailman/listinfo/marss86-devel >> >> >
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