Re: [Gems-users] Owner state in MOESI_CMP_directory protocol

["Liqun Cheng" <liqun.cheng@xxxxxxxxx>]

I grab this one, as Mike and Bradford are already overloaded. ;)
Owned state is not used to avoid invalidations, it is for reduce
(write-back) traffic. In the MESI, a processor needs to update memory
when it transitions from Modified to Shared during a snoop request.
With Owned state, the processor transitions from Modified to Owned
without updating the memory. The memory update is delayed until the
line in Owned state is evicted.
Owned state can also speedup read request in some protocols where
cache-to-cache transfer is allowed for lines in Shared/Owned states.
More detailed can be found in Shubu or Milo's Ph.D dissertation. 

Cheers
Legion

On 4/27/06, Enric Herrero <enricherrero@xxxxxxxx> wrote:

Hi,

We have been working in the MOESI_CMP_directory
protocol and we have seen that when a L1 cache is in
the Owned state and wants to modify the block then it
goes to the Modified state and the other sharers are
invalidated.
We think that the Owned state was used for avoiding
invalidations in the other sharers, by broadcasting
every change that makes. If it has to invalidate then
is the same as another sharer and the owned state is
not necessary, isn't it?
Thank you

/Marco and Enric




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