mem-ruby: Reduce handshaking between CorePair and dir #1117
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mattsinc
requested changes
May 9, 2024
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FYI, I may not get to this until next week |
@NSurawar has changes to make from my suggestions already, so no worries. |
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@NSurawar can you please wrap the changes up this week? |
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@NSurawar : you'll also need to update this branch to the head of develop before this can be committed. |
abmerop
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May 21, 2024
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| //Deprecated - WriteBack data (wb_data) is now sent with VicDirty itself | ||
| //Leaving this in for reference | ||
| assert(0); |
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I would just remove this. The error below should tell you which message type is missing
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I'm sorry for the delay. I was caught up in some other work. |
Currently when data is downgraded by MOESI_AMD_Base-CorePair (e.g. due to a replacement) this requires a 4-way handshake between the CorePair and the dir. Specifically, the CorePair send a message telling the dir it'd like to downgrade then, the dir sends an ACK back and then, the CorePair writes the data back, and finally, the dir ACKs the writeback. This is very inefficient and not representative of how modern protocols downgrade a request. Accordingly, this commits updates the downgrade support such that the CorePair writes back the data immediately and then the dir ACKs it. Thus, this approach requires only a 2-way handshake. Change-Id: I7ebc85bb03e8ce46a8847e3240fc170120e9fcd6
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I've removed the stale code now. Please let me know if any additional changes are required. |
abmerop
approved these changes
May 29, 2024
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Thanks all for getting this across the line while I was away |
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Currently when data is downgraded by MOESI_AMD_Base-CorePair (e.g. due to a replacement) this requires a 4-way handshake between the CorePair and the dir. Specifically, the CorePair send a message telling the dir it'd like to downgrade then, the dir sends an ACK back and then, the CorePair writes the data back, and finally, the dir ACKs the writeback.
This is very inefficient and not representative of how modern protocols downgrade a request. Accordingly, this commits updates the downgrade support such that the CorePair writes back the data immediately and then the dir ACKs it.
Thus, this approach requires only a 2-way handshake.
Change-Id: I7ebc85bb03e8ce46a8847e3240fc170120e9fcd6