Hi Andreas, iMHO, There are a couple of cases where it may not be required to invalidate line in lower levels
1. Inclusive caches: I would assume that the lower level inclusive caches should , by definition of inclusiveness, hold all the lines a higher level cache has. 2. Shared last level cache: the last level cache (the cache just ahead of main memory) may choose to not invalidate the line on a upgradereq. Rational: as long as exclusivity is maintained by private cache in earlier level, share LLC is strictly not required to invalidate the line on upgradereq. Kindly correct me if implicit assumptions I am making is distorting the reasoning:) Thanks and regards Nizam Sent from my iPad > On 04-Jan-2015, at 6:15 pm, Andreas Hansson <[email protected]> wrote: > > Hi Nizam, > > What do you suggest the lower-level cache should do? The UpgradeReq is > ultimately there to ensure that a cache can get a line in exclusive state (E) > to perform a write (M). > > Andreas > > From: Nizamudheen Ahmed via gem5-users <[email protected]> > Reply-To: Nizamudheen Ahmed <[email protected]>, gem5 users mailing list > <[email protected]> > Date: Sunday, 4 January 2015 08:47 > To: gem5 users mailing list <[email protected]> > Subject: [gem5-users] UpgradeReq command and impact on next-level cache > > Hi, > > I am using classic memory-model in GEM5. I observed that an UpgradeReq > command invalidates the line in cache. This behavior is acceptable for > peer-caches in the same-level. However, i am not sure if the UpgradeReq > should invalidate the cache line in the lower level caches (Caches closer to > the main-memory are lower levels, in my terminology). Can someone through > light on this? > > BR/Nizam > > > -- 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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