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This patch extends the classic prefetcher to work on non-block aligned
addresses. Because the existing prefetchers in gem5 mask off the lower
address bits of cache accesses, many predictable strides fail to be
detected. For example, if a load were to stride by 48 bytes, with 64 byte
cachelines, the current stride based prefetcher would see an access pattern
of 0, 64, 64, 128, 192.... Thus not detecting a constant stride pattern. This
patch fixes this, by training the prefetcher on access and not masking off the
lower address bits.
It also adds the following configuration options:
1) Training/prefetching only on cache misses,
2) Training/prefetching only on data acceses,
3) Optionally tagging prefetches with a PC address.
#3 allows prefetchers to train off of prefetch requests in systems with
multiple cache levels and PC-based prefetchers present at multiple levels.
It also effectively allows a pipelining of prefetch requests (like in POWER4)
across multiple levels of cache hierarchy.
Improves performance on my gem5 configuration by 4.3% for SPECINT and 4.7% for SPECFP (geomean).
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This patch adds the basic building blocks required to support e.g. ARM
TrustZone by discerning secure and non-secure memory accesses.
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This patch removes the time field from the packet as it was only used
by the preftecher. Similar to the packet queue, the prefetcher now
wraps the packet in a deferred packet, which also has a tick
representing the absolute time when the packet should be sent.
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This patch changes the cache-related latencies from an absolute time
expressed in Ticks, to a number of cycles that can be scaled with the
clock period of the caches. Ultimately this patch serves to enable
future work that involves dynamic frequency scaling. As an immediate
benefit it also makes it more convenient to specify cache performance
without implicitly assuming a specific CPU core operating frequency.
The stat blocked_cycles that actually counter in ticks is now updated
to count in cycles.
As the timing is now rounded to the clock edges of the cache, there
are some regressions that change. Plenty of them have very minor
changes, whereas some regressions with a short run-time are perturbed
quite significantly. A follow-on patch updates all the statistics for
the regressions.
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This change adds a master id to each request object which can be
used identify every device in the system that is capable of issuing a request.
This is part of the way to removing the numCpus+1 stats in the cache and
replacing them with the master ids. This is one of a series of changes
that make way for the stats output to be changed to python.
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cache
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This prevents redundant prefetches from being issued, solving the
occasional 'needsExclusive && !blk->isWritable()' assertion failure
in cache_impl.hh that several people have run into.
Eliminates "prefetch_cache_check_push" flag, neither setting of
which really solved the problem.
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Apparently we broke it with the cache rewrite and never noticed.
Thanks to Bao Yungang <baoyungang@gmail.com> for a significant part
of these changes (and for inspiring me to work on the rest).
Some other overdue cleanup on the prefetch code too.
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--HG--
rename : src/mem/cache/base_cache.cc => src/mem/cache/base.cc
rename : src/mem/cache/base_cache.hh => src/mem/cache/base.hh
rename : src/mem/cache/cache_blk.cc => src/mem/cache/blk.cc
rename : src/mem/cache/cache_blk.hh => src/mem/cache/blk.hh
rename : src/mem/cache/cache_builder.cc => src/mem/cache/builder.cc
rename : src/mem/cache/miss/mshr.cc => src/mem/cache/mshr.cc
rename : src/mem/cache/miss/mshr.hh => src/mem/cache/mshr.hh
rename : src/mem/cache/miss/mshr_queue.cc => src/mem/cache/mshr_queue.cc
rename : src/mem/cache/miss/mshr_queue.hh => src/mem/cache/mshr_queue.hh
rename : src/mem/cache/prefetch/base_prefetcher.cc => src/mem/cache/prefetch/base.cc
rename : src/mem/cache/prefetch/base_prefetcher.hh => src/mem/cache/prefetch/base.hh
rename : src/mem/cache/prefetch/ghb_prefetcher.cc => src/mem/cache/prefetch/ghb.cc
rename : src/mem/cache/prefetch/ghb_prefetcher.hh => src/mem/cache/prefetch/ghb.hh
rename : src/mem/cache/prefetch/stride_prefetcher.cc => src/mem/cache/prefetch/stride.cc
rename : src/mem/cache/prefetch/stride_prefetcher.hh => src/mem/cache/prefetch/stride.hh
rename : src/mem/cache/prefetch/tagged_prefetcher.cc => src/mem/cache/prefetch/tagged.cc
rename : src/mem/cache/prefetch/tagged_prefetcher.hh => src/mem/cache/prefetch/tagged.hh
rename : src/mem/cache/tags/base_tags.cc => src/mem/cache/tags/base.cc
rename : src/mem/cache/tags/base_tags.hh => src/mem/cache/tags/base.hh
rename : src/mem/cache/tags/Repl.py => src/mem/cache/tags/iic_repl/Repl.py
rename : src/mem/cache/tags/repl/gen.cc => src/mem/cache/tags/iic_repl/gen.cc
rename : src/mem/cache/tags/repl/gen.hh => src/mem/cache/tags/iic_repl/gen.hh
rename : src/mem/cache/tags/repl/repl.hh => src/mem/cache/tags/iic_repl/repl.hh
extra : convert_revision : ff7a35cc155a8d80317563c45cebe405984eac62
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