Majid Jalili has submitted this change. (
https://gem5-review.googlesource.com/c/public/gem5/+/56265 )
Change subject: mem-cache: adding round-robin aribitration to
multiprefetchers
......................................................................
mem-cache: adding round-robin aribitration to multiprefetchers
To find a candidate in cache base.cc, function getPacket
is called. In case of multi-prefetchers, we alyways start
from the first prefetcher. Given the default value for "latency"
is 1, there is always a candidate ready for prefech by prefetcher 0.
Hence, we need an arbitration mechansim to cycle through
all prefechers. To make this fair, we added a variable to save what
prefetcher first used to get a packet from, and in the next round,
we start from the next prefetcher to give every prefetcher a chance
to be the first one in a round-robin fashion.
JIRA Ticket: https://gem5.atlassian.net/browse/GEM5-1169
Change-Id: I1c6a267b2bf71764559a080371c1d7f8be95ac71
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56265
Reviewed-by: Daniel Carvalho <oda...@yahoo.com.br>
Maintainer: Daniel Carvalho <oda...@yahoo.com.br>
Tested-by: kokoro <noreply+kok...@google.com>
---
M src/mem/cache/prefetch/multi.cc
M src/mem/cache/prefetch/multi.hh
2 files changed, 38 insertions(+), 5 deletions(-)
Approvals:
Daniel Carvalho: Looks good to me, approved; Looks good to me, approved
kokoro: Regressions pass
diff --git a/src/mem/cache/prefetch/multi.cc
b/src/mem/cache/prefetch/multi.cc
index 230db50..ddf0e30 100644
--- a/src/mem/cache/prefetch/multi.cc
+++ b/src/mem/cache/prefetch/multi.cc
@@ -48,7 +48,8 @@
Multi::Multi(const MultiPrefetcherParams &p)
: Base(p),
- prefetchers(p.prefetchers.begin(), p.prefetchers.end())
+ prefetchers(p.prefetchers.begin(), p.prefetchers.end()),
+ lastChosenPf(0)
{
}
@@ -73,14 +74,18 @@
PacketPtr
Multi::getPacket()
{
- for (auto pf : prefetchers) {
- if (pf->nextPrefetchReadyTime() <= curTick()) {
- PacketPtr pkt = pf->getPacket();
+ lastChosenPf = (lastChosenPf + 1) % prefetchers.size();
+ uint8_t pf_turn = lastChosenPf;
+
+ for (int pf = 0 ; pf < prefetchers.size(); pf++) {
+ if (prefetchers[pf_turn]->nextPrefetchReadyTime() <= curTick()) {
+ PacketPtr pkt = prefetchers[pf_turn]->getPacket();
panic_if(!pkt, "Prefetcher is ready but didn't return a
packet.");
prefetchStats.pfIssued++;
issuedPrefetches++;
return pkt;
}
+ pf_turn = (pf_turn + 1) % prefetchers.size();
}
return nullptr;
diff --git a/src/mem/cache/prefetch/multi.hh
b/src/mem/cache/prefetch/multi.hh
index 037d23e..ff17918 100644
--- a/src/mem/cache/prefetch/multi.hh
+++ b/src/mem/cache/prefetch/multi.hh
@@ -38,6 +38,8 @@
#ifndef __MEM_CACHE_PREFETCH_MULTI_HH__
#define __MEM_CACHE_PREFETCH_MULTI_HH__
+#include <vector>
+
#include "mem/cache/prefetch/base.hh"
namespace gem5
@@ -70,7 +72,8 @@
protected:
/** List of sub-prefetchers ordered by priority. */
- std::list<Base*> prefetchers;
+ std::vector<Base*> prefetchers;
+ uint8_t lastChosenPf;
};
} // namespace prefetch
--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I1c6a267b2bf71764559a080371c1d7f8be95ac71
Gerrit-Change-Number: 56265
Gerrit-PatchSet: 5
Gerrit-Owner: Majid Jalili <majid0jal...@gmail.com>
Gerrit-Reviewer: Daniel Carvalho <oda...@yahoo.com.br>
Gerrit-Reviewer: Majid Jalili <majid0jal...@gmail.com>
Gerrit-Reviewer: Nikos Nikoleris <nikos.nikole...@arm.com>
Gerrit-Reviewer: kokoro <noreply+kok...@google.com>
Gerrit-MessageType: merged
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