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feat(Prefetcher): add CDP prefetcher in L2 - #15

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feat-l2-cdp
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feat(Prefetcher): add CDP prefetcher in L2#15
ChrisYzcc wants to merge 46 commits into
masterfrom
feat-l2-cdp

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@ChrisYzcc ChrisYzcc commented Jun 11, 2026 •
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Summary

This PR implements a Content-Directed Prefetcher (CDP) in the L2 cache to improve performance for pointer-chasing workloads.

Main changes

  • Add the CDP prefetcher implementation (coupledL2/prefetch/CDP.scala).
  • Add CDP detection trigger logic to MainPipe.
  • Add CDP training trigger logic to MainPipe, and classify prefetch training destination types using is_cdp_train and is_other_train in the PrefetchTrain bundle.
  • Add the pfDepth field to the cacheline metadata.
  • Add PrefetcherMonitor to support accuracy-based dynamic tuning for CDP (currently disabled).
  • Add a dedicated PrefetchTrain request buffer for each prefetcher in prefetch/Prefetcher.scala.
  • Add TLB request arbitration between BOP and CDP in prefetch/Prefetcher.scala.

Performance

On the SPEC CPU2006 GCC15 0.3c checkpoint suite, CDP achieves:

  • +1.58% integer score
  • +0.57% overall score
{0CCB9E9D-4A4B-4F95-804E-9C90815DC9AC}

@ChrisYzcc
ChrisYzcc requested a review from Copilot July 13, 2026 09:23

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@ChrisYzcc
ChrisYzcc force-pushed the feat-l2-cdp branch 2 times, most recently from 3c0677c to 7713c73 Compare July 14, 2026 04:34
ChrisYzcc added 24 commits July 16, 2026 16:44
@ChrisYzcc
feat(CDP): init for trasfering CDP from origin coupledL2
088fabb
@ChrisYzcc
fix(CoupledL2): fix missing bits in evict block addr
342184e
@ChrisYzcc
feat(CDP): change the position of degree buffer
409e650
@ChrisYzcc
feat(CDP): add batched tlb req
7985fc0
@ChrisYzcc
feat(CDP): add perf counters for monitoring trigger source
fc0b19b
@ChrisYzcc
feat(CDP): enable FilteredDetect for test
e0e65b1
@ChrisYzcc
Revert "feat(CDP): enable FilteredDetect for test"
ba69f19 
This reverts commit 3bca141.
@ChrisYzcc
feat(CDP): set config to (degree=3, entryBits=20, UseFiltered=0) for …
2520534 
…test
@ChrisYzcc
fix(CDP): fix tlb handshake problem in SentUnit tlb req pipeline
21233d3
@ChrisYzcc
Revert "feat(CDP): set config to (degree=3, entryBits=20, UseFiltered…
824f36d 
…=0) for test"

This reverts commit d924d27.
@ChrisYzcc
chore(MainPipe, MSHR): use .getOrElse instead of .get
367e5e5
@ChrisYzcc
fix(CoupledL2): connect cdp_trigger
669fd28
@ChrisYzcc
feat(CDP): add pfStat for dynamic degree
34ba847
@ChrisYzcc
feat(CDP): add DynamicDegree switch and perf counter
25746fa
@ChrisYzcc
feat(CDP): use EWMA for dynamic accuracy
886b349
@ChrisYzcc
fix(Prefetcher): add train buf for each prefetcher to avoid unclear c…
bae25f4 
…onnection of io.train
@ChrisYzcc
feat(CDP): add perf counter to monitor the number of dropped train re…
01ab3a7 
…quests
@ChrisYzcc
feat(CDP): disable dynamic degree for test
a626d02
@ChrisYzcc
submodule(utility): bump for utility
658d171
@ChrisYzcc
fix(Prefetcher): fix wrong train trigger of CDP due to rebase
f26cb3c
@ChrisYzcc
fix(Prefetcher): remove wrong condition check which will filter merge…
b9b51cc 
…A train triggers
@ChrisYzcc
feat(CDP, Prefetcher): support parameterized CDP trigger num
9216ffc
@ChrisYzcc
feat(CDP): add dynamic switch for FilterTable
54fddb0
@ChrisYzcc
feat(CDP): add perf counter to monitro dropped req in SentUnit
2850a10
@ChrisYzcc ChrisYzcc changed the title feat(CDP): add CDP prefetcher in L2 feat(Prefetcher): add CDP prefetcher in L2 Jul 19, 2026
@ChrisYzcc ChrisYzcc reopened this Jul 19, 2026
@ChrisYzcc
ChrisYzcc marked this pull request as ready for review July 19, 2026 06:16
@linjuanZ
linjuanZ requested a review from Ma-YX July 21, 2026 07:54
Ma-YX
Ma-YX reviewed Jul 21, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
linjuanZ
linjuanZ requested changes Jul 21, 2026
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Comment thread src/main/scala/coupledL2/prefetch/Prefetcher.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/Prefetcher.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/Prefetcher.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/Prefetcher.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/Prefetcher.scala Outdated
Comment thread src/main/scala/coupledL2/MainPipe.scala Outdated
Comment thread src/main/scala/coupledL2/MainPipe.scala
Comment thread src/main/scala/coupledL2/MainPipe.scala Outdated
Comment thread src/main/scala/coupledL2/MainPipe.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/PrefetcherMonitor.scala Outdated
Ma-YX
Ma-YX reviewed Jul 21, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala
Ma-YX
Ma-YX reviewed Jul 21, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala
Ma-YX
Ma-YX reviewed Jul 21, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
linjuanZ
linjuanZ reviewed Jul 22, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
linjuanZ
linjuanZ requested changes Jul 22, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
linjuanZ
linjuanZ requested changes Jul 22, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
Comment thread src/main/scala/coupledL2/prefetch/CDP.scala Outdated
ChrisYzcc added 6 commits July 22, 2026 19:22
@ChrisYzcc
fix(CDP, Prefetcher): let selector decide the priority of the prefetc…
d350611 
…h requests; let CSR signal control CDP enable
@ChrisYzcc
refactor(CDP): unify detect tasks and refine VPN table validity
627a352 
Consolidate CDP detect pipeline payloads into a width-parameterized task bundle. Track VPN main-entry and sub-entry validity separately, initialize metadata on allocation, and simplify pipeline register handling.
@ChrisYzcc
refactor(CDP): standardize naming conventions
a73df56
@ChrisYzcc
feat(CDP): parameterize retryInterval in SentUnit
1657fac
@ChrisYzcc
refactor(PrefetchMonitor): remove redundant code
0152c6c
@ChrisYzcc
refactor(Prefetcher): use Arbiter for TLB arbitration logic
96fb08e
Ma-YX
Ma-YX reviewed Jul 24, 2026
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Comment thread src/main/scala/coupledL2/prefetch/CDP.scala
@ChrisYzcc
ChrisYzcc requested a review from linjuanZ July 27, 2026 01:06
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