Inclusive L3? Wow

Article: ISSCC 2006: Intel Tulsa
By: Michael S (, February 21, 2006 11:03 am
Room: Moderated Discussions
Linus Torvalds ( on 2/21/06 wrote:
>Michael S ( on 2/21/06 wrote:
>>It should be rather complex to build inclusive cache that
>>has to stay in synch with not one, not two, but SIX inner
>Why would that be complex? I think the Intel L2 is already
>inclusive, and so the L3 can totally ignore the L1 I/D side
>entirely. So there are just two inner caches that it needs
>to worry about.
>And the L3 would have to be inclusive if you want all the
>coherency logic to be there, and not have to worry about
>snooping the L2. Makes perfect sense to me.
>Or am I missing something?

Yes, you are missing the fact that L2 is not inclusive.

From the latest IA-32 Intel Architecture Optimization Reference Manual:
"Levels in the cache hierarchy are not inclusive. The fact that a line is in level i does not imply that it is also in level i+1. All caches use a pseudo-LRU (least recently used) replacement algorithm."
p. 1.20.

Changing L2 cache policy to inclusive would constitute rather big change in the Netburst microarchitecture hardly justifiable by needs of the single low-volume member of the family, especially taking into account that it is most likely the last member.

< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Intel Tulsa Coverage from ISSCCDavid Kanter2006/02/21 02:45 AM
  Intel Tulsa Coverage from ISSCCAlberto2006/02/21 04:43 AM
    Intel Tulsa Coverage from ISSCCPaul DeMone2006/02/21 06:52 AM
  Inclusive L3? WowMichael S2006/02/21 04:51 AM
    Inclusive L3? WowWouter Tinus2006/02/21 07:06 AM
      Inclusive L3? WowMichael S2006/02/21 08:20 AM
        Inclusive L3? Wowslim2006/02/21 11:40 AM
    It is?anonymous2006/02/21 09:57 AM
    Inclusive L3? WowLinus Torvalds2006/02/21 10:10 AM
      Inclusive L3? WowMichael S2006/02/21 11:03 AM
        Inclusive L3? WowLinus Torvalds2006/02/21 11:52 AM
          Inclusive L3? WowEric Bron2006/02/22 06:39 AM
            Inclusive L3David Kanter2006/02/22 12:16 PM
              Inclusive L3Eric Bron2006/02/22 01:00 PM
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