... | @@ -175,6 +175,6 @@ The results show: |
... | @@ -175,6 +175,6 @@ The results show: |
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2. The L2 writeback path can be characterized. No information about L3 writebacks.
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2. The L2 writeback path can be characterized. No information about L3 writebacks.
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3. No information about the load path (##)
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3. No information about the load path (##)
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So, if we leave out the `L2_TRANS_L2_WB` from the `L3` performance group, we can include both `IDI_MISC_WB*` events and still have one counter register left. In this counter we could measure the L3 hits to characterize the load path. Unfortunately, the `MEM_LOAD_L3_*` are likely to be listed in the specification updates. This is not the case for Intel Skylake SP but for Intel Skylake Desktop.
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So, if we leave out the `L2_TRANS_L2_WB` from the `L3` performance group, we can include both `IDI_MISC_WB*` events and still have one counter register left. In this counter we could measure the L3 hits to characterize the load path. Unfortunately, the `MEM_LOAD_L3_*` are likely to be listed in the specification updates. This is not the case for [Intel Skylake SP](https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-scalable-spec-update.pdf) but for [Intel Skylake Desktop (SKL128)](https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/desktop-6th-gen-core-family-spec-update.pdf).
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(##) Commonly, all data should be loaded from memory directly to L2 except the LLC prefetcher is active (like in this case). One might assume that all cache lines evicted to L3 for re-use are also loaded again from L3 but that would mean that the heuristics are always the optimal decision. |
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(##) Commonly, all data should be loaded from memory directly to L2 except the LLC prefetcher is active (like in this case). One might assume that all cache lines evicted to L3 for re-use are also loaded again from L3 but that would mean that the heuristics are always the optimal decision. |
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