ipmctl MediaReads and MediaWrites vs. 256B granularity

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kanwu...@gmail.com

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Sep 21, 2021, 5:38:23 PM9/21/21
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Hi there,

I have a question related to media counters reported by ipmctl vs. PMEM 256B granularity:
  • does MediaReads and MediaWrites counters  count the access amplification?
  • in other words, assuming there is a 64B load to the DIMM (and I assume it will be amplified to a 256B load), then would the counter count 4 x 64B?
thank you

Kan

Andy Rudoff

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Sep 22, 2021, 10:14:10 AM9/22/21
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This question was answered on our Slack channel.  Copying the answer here so it pops up in future searches...

Our media reads stat is in cachelines, So you will see a 4X amplification on our current Optane PMem products. Typically for writes you will see 2X but sometimes more or less depending on merging of writes. We do have a 256B read buffer so sequential cachelines might hit that buffer and not result in an amplification.

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