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mem-cache: add a prefetch useful stat

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Count how many time a prefetch is useful, meaning
a hit has happened on a prefetched cache block.
Another stat (pfUsefulButMiss) has been added to count
the special case where there is a hit on prefetched block
but it is counted as a miss because the block is not in
the requested coherency state.

Change-Id: I253216b9ac96d5f21139b710c489d6eb3fce7136
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47602
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Daniel Carvalho <odanrc@yahoo.com.br>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Nathanael Premillieu
2021-06-30 15:00:06 +02:00
parent f691613876
commit c66f32f24e
2 changed files with 16 additions and 1 deletions
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12
src/mem/cache/prefetch/base.cc vendored
View File

@@ -122,7 +122,12 @@ Base::StatGroup::StatGroup(statistics::Group *parent)
ADD_STAT(pfIssued, statistics::units::Count::get(),
"number of hwpf issued"),
ADD_STAT(pfUnused, statistics::units::Count::get(),
"number of HardPF blocks evicted w/o reference")
"number of HardPF blocks evicted w/o reference"),
ADD_STAT(pfUseful, statistics::units::Count::get(),
"number of useful prefetch"),
ADD_STAT(pfUsefulButMiss, statistics::units::Count::get(),
"number of hit on prefetch but cache block is not in an usable "
"state")
{
pfUnused.flags(statistics::nozero);
}
@@ -219,6 +224,11 @@ Base::probeNotify(const PacketPtr &pkt, bool miss)
if (hasBeenPrefetched(pkt->getAddr(), pkt->isSecure())) {
usefulPrefetches += 1;
prefetchStats.pfUseful++;
if (miss)
// This case happens when a demand hits on a prefetched line
// that's not in the requested coherency state.
prefetchStats.pfUsefulButMiss++;
}
// Verify this access type is observed by prefetcher

5
src/mem/cache/prefetch/base.hh vendored
View File

@@ -332,6 +332,11 @@ class Base : public ClockedObject
/** The number of times a HW-prefetched block is evicted w/o
* reference. */
statistics::Scalar pfUnused;
/** The number of times a HW-prefetch is useful. */
statistics::Scalar pfUseful;
/** The number of times there is a hit on prefetch but cache block
* is not in an usable state */
statistics::Scalar pfUsefulButMiss;
} prefetchStats;
/** Total prefetches issued */