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2019-10-29mem-cache: Add a repeated value pattern to compressorsDaniel R. Carvalho
The repeated value pattern checks if values are composed of multiple instances of the same value. If successful, the bits of the repeated value are included only once in the compressed data. Change-Id: Ia7045b4e33a91fd8d712fe1ca689f7f8cb4e5feb Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21153 Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-29mem-cache: Inform unused bits instead of bytes in compressor patternDaniel R. Carvalho
Increase pattern precision by giving the number of unmatched bits instead of bytes. Change-Id: I5efbe9c31672cc973b4c89c741cdc8cc28d26285 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21152 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-29mem-cache: Add a masked const value pattern to compressorsDaniel R. Carvalho
The masked pattern compares values to masked const non-dictionary values to determine whether these match. If successful, the bits that do not match must be added to the compressed data. Change-Id: I4c53568694dab916136fe384cb2ee10e554f7136 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21151 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-29mem-cache: Add a masked pattern to compressorsDaniel R. Carvalho
The masked pattern compares masked values to masked dictionary entries to determine whether these values match. If successful, the bits that do not match must be added to the compressed data. Change-Id: I4b1c8feb0faa99576382b54a73a20c353f965d2a Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21150 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-29mem-cache: Add an uncompressed pattern to compressorsDaniel R. Carvalho
The uncompressed pattern always stores the original data, and therefore it is always successful. All of the derived classes of the dictionary compressor must have this pattern as the last pattern of the pattern factory. Change-Id: I2a38fd56630d88ef8b918220dc4c2824a196a8a2 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21149 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-29mem-cache: Templatize DictionaryCompressorDaniel R. Carvalho
Templatize DictionaryCompressor so that the dictionary entries' sizes can be changed. Change-Id: I3d89e3c692a721cefcd7e3c55d2ccdefa425f614 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21148 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-10-29mem-cache: Factor out CPack's dictionary functionalityDaniel R. Carvalho
Factor out dictionary functionality of CPack, so that it can be used easily for other compressors. As a side effect, create an addToDictionary function to allow subclasses to chose how to handle insertion. Change-Id: I02fae4e98b02db5a40467ec470b71020d5e867cb Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21147 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
2019-10-29mem-cache: Use shouldAllocate() instead of CPack's decompress()Daniel R. Carvalho
Split decompression functionality using the proper function to determine if a dictionary entry should be allocated after decompression or not. Change-Id: I4995304f4c4508c03c9fc1685f04511622969556 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21146 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-10-29mem-cache: Limit compression sizeDaniel R. Carvalho
Add a threshold so that if the compressed size is greater than it, the compression is abandoned, and the data is considered uncompressible. Change-Id: Ic416195b06ec440a40263b75bd0f0383cde2ea6a Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21144 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-10-29mem-cache: Do not try to compress dataless packetsDaniel R. Carvalho
Fix filling blocks so that packets that do not contain data do not generate a compression attempt. This can happen, for example, with invalidation responses, which will trigger a packet data access assertion. Change-Id: I2a1e7983657f6e5e770b148ab62c9de9ac3986ac Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22164 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-29mem-cache: Avoid promotion of incompatible deferred targetsNikos Nikoleris
Often a request that hits on an MSHR has to be deferred as it can't be serviced by the current response. For example, a request that requires writable has to be deferred when the response is expected to bring in a read-only copy of the block. However, there are cases where the response, although not expected to do so, brings a writable copy and as a result we also service deferred targets. In such cases, we promote deferred targets up until the first that can't be serviced by the current response (e.g., cache maintainance operation). If the first deferred target is incompatible we don't promote any targets at all. Change-Id: Ib3e13be51120b7c0f0053b83b76bde03e1b7dd4e Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22127 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Jason Lowe-Power <jason@lowepower.com>
2019-10-29mem-cache: Fix MSHR whole line write trackingNikos Nikoleris
The MSHR keeps track of outstanding writes and services them as a whole line write whenever possible. To do this the outstanding writes have to be compatible (e.g., not strictly ordered). Prior to this change, due to this tracking mechanism, the MSHR would not service a WriteLineReq with flags that do not allow merging as a full line write even if it was the first target triggering an assertion. This changeset fixes this bug. Change-Id: I2cbf5ece0c108c1fcfe6855e8f194408d5ab8ce2 Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22126 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-13mem-cache: set the second chance to false when inserting a blockMingyuan
Modify second chance replacement policy so that entries are inserted without a second chance. Previously, the second chance bit was set to true when a cache line was inserted. So the cache line would gain its second chance when inserting. This is wrong because the cache block will only get a second chance when it hits. Here's a quoted citation for the second chance replacement policy: "Whenever the algorithm examines a page entry, it extracts the associated usage bit and enters it into the high-order position of a k-bit shift register after shifting the contents of the register one bit-position lower. Then if the shift register is nonzero, the page is retained; if the shift register is zero, the page is replaced by the new page. In either case the usage bit for the page is turned off and the circular list pointer is advanced." (A Paging Experiment with the Multics System, FJ Corbato, 1968) Change-Id: I0d07e56aa16c67dd36e0d490c3f457f91e46f320 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20882 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Jason Lowe-Power <jason@lowepower.com>
2019-10-12mem-cache: Fixed a bug in MRU replacement policyMingyuan
The lastTouchTick is set to 0 when instantiate. This will cause the candidate[0] to get evicted over and over again in MRU replacement policy. To resolve this, break the search loop whenever it finds a cold cache line. Change-Id: I33aa57ebe0efca15986f62c3ae10a146bd2b779f Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20881 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
2019-10-11mem-ruby: Allow Ruby to use all replacement policies in ClassicJingQuJQ
Add support in Ruby to use all replacement policies in Classic. Furthermore, if new replacement policies are added to the Classic system, the Ruby system will recognize new policies without any other changes in Ruby system. The following list all the major changes: * Make Ruby cache entries (AbstractCacheEntry) inherit from Classic cache entries (ReplaceableEntry). By doing this, replacement policies can use cache entries from Ruby caches. AccessPermission and print function are moved from AbstractEntry to AbstractCacheEntry, so AbstractEntry is no longer needed. * DirectoryMemory and all SLICC files are changed to use AbstractCacheEntry as their cache entry interface. So do the python files in mem/slicc/ast which check the entry interface. * "main='false'" argument is added to the protocol files where the DirectoryEntry is defined. This change helps differentiate DirectoryEntry from CacheEntry because they are both the instances of AbstractCacheEntry now. * Use BaseReplacementPolicy in Ruby caches instead of AbstractReplacementPolicy so that Ruby caches will recognize the replacement policies from Classic. * Add getLastAccess() and useOccupancy() function to Classic system so that Ruby caches can use them. Move lastTouchTick to ReplacementData struct because it's needed by getLastAccess() to return the correct value. * Add a 2-dimensional array of ReplacementData in Ruby caches to store information for different replacement policies. Note that, unlike Classic caches, where policy information is stored in cache entries, the policy information needs to be stored in a new 2-dimensional array. This is due to Ruby caches deleting the cache entry every time the corresponding cache line get evicted. Change-Id: Idff6fdd2102a552c103e9d5f31f779aae052943f Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20879 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-10-01mem-cache: Fix invalid whenReadyDaniel R. Carvalho
When a writeback needs to be allocated the whenReady field of the block is not set, and therefore its access latency calculation uses the previously invalidated value (MaxTick), significantly delaying execution. This is fixed by assuming that the data write portion of a write access is done regardless of previous writes, and that only the tag latency is important for the critical path latency calculation. Change-Id: I739132a2deab6eb4c46d084f4ee6dd65177873fd Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20068 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-09-30mem-cache: Switch to new-style statsAndreas Sandberg
This change puts cache and tag stats into a Stats::Group struct. This makes it easier to identify stat updates (they are prefixed with stat.) and adds hierarchy information for output formats that need it. Change-Id: I2b8e9138f1cb977abb445ec864d80a79b588481d Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21140 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-09-12mem-cache: Fix BDI size calculationDaniel R. Carvalho
The bitmask field indicates to which base a delta refers, and in the original paper it is fixed and proportional to the highest number of bases allowed in the compressed data. Change-Id: I271bf2e19e0765de52b933eaf6d4fcc2ce25d185 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19748 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-08-29mem-cache: Use SatCounter for RRPVDaniel R. Carvalho
Use SatCounter in RRIP's RRPV. As such, move validation functionality to a proper variable. Change-Id: I142db2b7f6cd518ac3a2b68c9ed48005402b3464 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20452 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-08-28mem: Eliminate the Base(Slave|Master)Port classes.Gabe Black
The Port class has assumed all the duties of the less generic Base*Port classes, making them unnecessary. Since they don't add anything but make the code more complex, this change eliminates them. Change-Id: Ibb9c56def04465f353362595c1f1c5ac5083e5e9 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20236 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Gabe Black <gabeblack@google.com>
2019-08-07mem-cache: Fix non-virtual base destructor of Repl EntryDaniel R. Carvalho
ReplaceableEntry contains a virtual method, yet its destructor was not virtual, causing errors in some compilers. Change-Id: I13deec843f4007d9deb924882a8d98ff6a89c84f Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19808 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-07-31mem-cache: mark block as dirty when handling SW prefetchTiago Mück
This addresses the issue described in 64687ee mem-cache: Mark block as dirty after a SWPrefetchEXResp. Previous patch misses cases when the prefetch response is ReadExResp or UpgradeResp. Also, marking the block as dirty in serviceMSHRTargets instead of in handleFill covers cases when the prefetch is coalesced with other requests. Change-Id: I2b377fdd240eb0f09e720b6bb284dee6545925ce Signed-off-by: Tiago Mück <tiago.muck@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19688 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-07-31mem-cache: Fix set and way of sub-entriesDaniel R. Carvalho
Set and way of sub-entries were not being set previously. They must be set after the sub-blocks have been assigned to the main block. Change-Id: I7b6921b8437b29c472d691cd78cf20f2bb6c7e07 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19669 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-07-17mem-cache: Create CPack compressorDaniel R. Carvalho
Implementation of C-Pack, as described in "C-Pack: A High- Performance Microprocessor Cache Compression Algorithm". C-Pack uses pattern matching schemes to detect and compress frequently appearing data patterns. As in the original paper, it divides the input in 32-bit words, and uses 6 patterns to match with its dictionary. For the patterns, each letter represents a byte: Z is a null byte, M is a dictionary match, X is a new value. The patterns are ZZZZ, XXXX, MMMM, MMXX, ZZZX, MMMX. Change-Id: I2efc9db2c862620dcc1155300e39be558f9017e0 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11105 Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-06-04Revert "mem-cache: Remove writebacks packet list"Daniel Carvalho
This reverts commit bf0a722acdd8247602e83720a5f81a0b69c76250. Reason for revert: This patch introduces a bug: The problem here is that the insertion of block A may cause the eviction of block B, which on the lower level may cause the eviction of block A. Since A is not marked as present yet, A is "safely" removed from the snoop filter However, by reverting it, using atomic and a Tags sub-class that can generate multiple evictions at once becomes broken when using Atomic mode and shall be fixed in a future patch. Change-Id: I5b27e54b54ae5b50255588835c1a2ebf3015f002 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19088 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-05-29mem-cache: Accuracy-based rate control for prefetchersJavier Bueno
Added a mechanism to control the number of prefetches generated based in the effectiveness of the prefetches generated so far. Change-Id: I33af82546f74a5b5ab372c28574b76dd9a1bd46a Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18808 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-29mem-cache: Support for page crossing prefetchesJavier Bueno
Prefetchers can now issue hardware prefetch requests that go beyond the boundaries of the system page. Page crossing references will need to look up the TLBs to be able to compute the physical address to be prefetched. Change-Id: Ib56374097e3b7dc87414139d210ea9272f96b06b Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/14620 Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-20mem-cache: Add multi-prefetcher adaptorAndreas Sandberg
This patch adds a meta-prefetcher that enables gem5's cache models to connect to multiple prefetchers. Sub-prefetchers still use the probes-based interface and training can be controlled independently. However, when the cache requests a prefetch packet, the adaptor traverses the priority list of prefetchers and uses the first prefetcher that is able to generate a prefetch. Kudos to Mitch Hayenga for the original version of this patch. Change-Id: I25569a834997e5404c7183ec995d212912c5dcdf Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18868 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-05-18arch, base, cpu, dev, mem, sim: Remove #if 0-ed out code.Gabe Black
This code will be preserved through version control, but otherwise creates clutter and will rot in place since it's never compiled. Change-Id: Id265f6deac445116843956ea5cf1210d8127274e Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18608 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Brandon Potter <Brandon.Potter@amd.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-05-14mem-cache: Use SatCounter for prefetchersDaniel
Many prefetchers re-implement saturating counters with ints. Make them use SatCounters instead. Added missing operators and constructors to SatCounter for that to be possible and their respective tests. Change-Id: I36f10c89c27c9b3d1bf461e9ea546920f6ebb888 Signed-off-by: Daniel <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17995 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Javier Bueno Hedo <javier.bueno@metempsy.com> Maintainer: Jason Lowe-Power <jason@lowepower.com>
2019-05-11cpu,mem: Add support for partial loads/stores and wide mem. accessesGiacomo Gabrielli
This changeset adds support for partial (or masked) loads/stores, i.e. loads/stores that can disable accesses to individual bytes within the target address range. In addition, this changeset extends the code to crack memory accesses across most CPU models (TimingSimpleCPU still TBD), so that arbitrarily wide memory accesses are supported. These changes are required for supporting ISAs with wide vectors. Additional authors: - Gabor Dozsa <gabor.dozsa@arm.com> - Tiago Muck <tiago.muck@arm.com> Change-Id: Ibad33541c258ad72925c0b1d5abc3e5e8bf92d92 Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/13518 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Remove writebacks packet listDaniel R. Carvalho
Previously all atomic writebacks concerned a single block, therefore, when a block was evicted, no other block would be pending eviction. With sector tags (and compression), however, a single replacement can generate many evictions. This can cause problems, since a writeback that evicts a block may evict blocks in the lower cache. If one of these conflict with one of the blocks pending eviction in the higher level, the snoop must inform it to the lower level. Since atomic mode does not have a writebuffer, this kind of conflict wouldn't be noticed. Therefore, instead of evicting multiple blocks at once, we do it one by one. Change-Id: I2fc2f9eb0f26248ddf91adbe987d158f5a2e592b Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18209 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Handle data expansionDaniel R. Carvalho
When a block in compressed form is overwriten, it may change its size. If the new compressed size is bigger, and the total size becomes bigger than the block size, one or more blocks will have to be evicted. This is called data expansion, or fat writes. This change assumes that a first level cache cannot have a compressor, since otherwise data expansion should have been handled for atomic operations and writes. As such, data expansions should only be seen on writebacks. As writebacks are forwarded to the next level when failed, there should be no data expansions when servicing misses either. This patch adds the functionality to handle data expansions by evicting the co-allocated blocks to make room for an expanded block. Change-Id: I0bd77bf6446bfae336889940b2f75d6f0c87e533 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/12087 Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-05-08mem-cache: Add co-allocation function to compressed tagsDaniel R. Carvalho
Implement a co-allocation function in compressed tags, so that compressed blocks can be co-allocated in a superblock. Co-allocation is possible when compression ratio (CR) blocks that share a superblock tag can be compressed to up to (100/CR)% of their size. Change-Id: I937cc1fcbb488e70309cb5478c12db65f1b4b23f Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11411 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Add compression and decompression callsDaniel R. Carvalho
Add a compressor to the base cache class and compress within block allocation and decompress on writebacks. This change does not implement data expansion (fat writes) yet, nor it adds the compression latency to the block write time. Change-Id: Ie36db65f7487c9b05ec4aedebc2c7651b4cb4821 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11410 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Create BDI CompressorDaniel R. Carvalho
Implement Base-Delta-Immediate compression, as described in 'Base-Delta-Immediate Compression: Practical Data Compression for On-Chip Caches' Change-Id: I7980c340ab53a086b748f4b2108de4adc775fac8 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11412 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Add compression statsDaniel R. Carvalho
Add compression statistics to the compressors. It tracks the number of blocks that can fit into a certain power of two size, and the number of decompressions. For example, if a block is compressed to 100 bits, it will belong to the 128-bits compression size. Although it could also fit bigger sizes, they are not taken into account for the stats (i.e., the 100-bit compression will fit only the 128-bits size, not 256 or higher). We save stats for compressions that fail (i.e., compressed size is bigger than original cache line size). Change-Id: Idab71a40a660e33259908ccd880e42a880b5ee06 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11103 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Create cache compressorDaniel R. Carvalho
Create basic template for cache compressors. A basic compressor must implement a compression and a decompression method. Change-Id: I83dc4d2b8d2bc5ed9f760c938edfa4ebdd6b8583 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11100 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Add block size to findVictimDaniel R. Carvalho
Add block size to findVictim. For standard caches it will not be used. Compressed caches, however, need to know the size of the compressed block to decide whether a block is co-allocatable or not. Change-Id: Id07f79763687b29f75d707c080fa9bd978a408aa Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11198 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Mohammad Seyedzadeh <sm.seyedzade@gmail.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Add compression data to CompressionBlkDaniel R. Carvalho
Add a compression bit, decompression latency and compressed block size and their respective getters and setters. Change-Id: Ia9d8656552d60e8d4e85fe5379dd75fc5adb0abe Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11102 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-08mem-cache: Create CacheComp debug flagDaniel R. Carvalho
Create a debug flag for cache compression. Change-Id: Id4b8e86d658d3aa550906ee0f8da3b54f4cdab7d Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/11104 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Jason Lowe-Power <jason@lowepower.com>
2019-05-08mem-cache: Stub compression frameworkDaniel R. Carvalho
Create a stub of a compression framework where we can have multiple data blocks per tag entry. Only consecutive blocks can share a tag as of now. For each tag entry there can be multiple data blocks. We have the same number of tags a conventional cache would have, but we instantiate the maximum number of data blocks (according to the compression ratio) per tag, to virtually implement compression without increasing the complexity of the simulator. Change-Id: I549940c7afb2f744ab293ff8bb283967e7551a11 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/10763 Tested-by: kokoro <noreply+kokoro@google.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-05-03mem-cache: Mark block as dirty after a SWPrefetchEXRespNikos Nikoleris
This is a workaround for a bug introduced from the change: 59e3585a8 arch-arm: We add PRFM PST instruction for arm which can cause deadlocks in the memory system. The design of the classic memory system in gem5 makes the folloing two assumptions: * A cache that fetches a block with an intention to modify it, becomes the point of ordering and therefore commits to respond to any snoop requests [1]. * A cache that fetches an exclusive copy of the block, does so with the intention to modify it [2]. Immediately after it receives the block, it will write to it and mark it as dirty. As the point of ordering, it responds to any outstanding snoops. The current implementation of prefetch exclusive request breaks the second assumption. A cache can fetch an exclusive block without an immediate intention to modify it. If the block is not modified, it will not be marked as dirty. However, the cache has committed to respond to outstanding snoops, and if the block is clean it won't. This can result in deadlocks where a snoop gets stuck waiting for responses. One solution (implemented by this patch) is to unconditionally mark the block dirty when filling due to a prefetch exclusive request. This makes the PrefetchExReq behave like a WriteReq. However, as it may mark as dirty a clean block, it creates the requirement for an uncessary WritebackDirty in the future. In practice, this shouldn't be a big problem unless the application is unnecessarily using prefetch exclusive instructions. Other solutions, would require deeper changes to the design of the memory system to handle this properly. [1]: When a cache commits to respond, it "informs" the xbar/PoC (point of coherence) and the other caches of its intention to respond. As a result the request will not be send to the main memory. [2]: In fact the assumption is that in the needsWritable MSHR there is at least one WriteReq before any snoops from other caches. Change-Id: I378d3c0dadf25fc52e430b67102347b44d2f18ea Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17729 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Tested-by: kokoro <noreply+kokoro@google.com>
2019-04-28mem: Minimize the use of MemObject.Gabe Black
MemObject doesn't provide anything beyond its base ClockedObject any more, so this change removes it from most inheritance hierarchies. Occasionally MemObject is replaced with SimObject when I was fairly confident that the extra functionality of ClockedObject wasn't needed. Change-Id: Ic014ab61e56402e62548e8c831eb16e26523fdce Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18289 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com> Maintainer: Gabe Black <gabeblack@google.com>
2019-04-24cpu,mem: missing override specifierAndrea Mondelli
Change-Id: I731d3ef021596450ac307461f215760a148bb28a Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18348 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-04-22mem-cache: Fix fix of replacement countDaniel
Commit 7976b561de61b7523ca9a860154ad7ba701d12a7 tried fixing replacement update when a single location can be associated to multiple blocks. Although the comment of the correct action was added, the proper validation check was forgotten. This change adds that check and moves doing the eviction to when there is a valid block. Change-Id: I31d8bb914ccfd1849e9d97464d70a58a62f59533 Signed-off-by: Daniel <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18210 Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Tested-by: kokoro <noreply+kokoro@google.com>
2019-04-19mem-cache: Fix increasing replacement countDaniel R. Carvalho
Replacements should be increased when there is any evicted block, which does not necessarily have to be the victim. For example, assume a superblock contains 4 blocks, and both A and C are stored compressed (belonging to SB_1). Then F, from SB2 needs to make room by replacing SB1. If F map to location 2, the number of replacements should be increased, even though 2 had no valid blocks: Tag Data Tag Data |SB_1|--|A|X|C|X| --> |SB_2| |X|F|X|X| 1 2 3 4 1 2 3 4 Change-Id: I7b3735d28a35faa8d8fa613a1555bb258da65859 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18208 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Maintainer: Jason Lowe-Power <jason@lowepower.com>
2019-04-19mem-cache: Remove blk_addr from Queue::trySatisfyFunctionalDaniel R. Carvalho
The blk_addr is pkt->getBlockAddr(), and therefore can be acquired internally, when needed, as long as the pkt is provided. Change-Id: I2780445d2a0cb9e27257961efc4f438cc19550e5 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17537 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-04-19mem-cache: Add match functions to QueueEntryDaniel R. Carvalho
Having the caller decide the matching logic is error-prone, and frequently ends up with the secure bit being forgotten. This change adds matching functions to the QueueEntry to avoid this problem. As a side effect the signature of findPending has been changed. Change-Id: I6e494a821c1e6e841ab103ec69632c0e1b269a08 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17530 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
2019-04-19mem: Add packet matching functionsDaniel R. Carvalho
Add both block and non-block-aligned packet matching functions, so that both address and secure bits are checked when checking whether a packet matches a request. Change-Id: Id0069befb925d112e06f250741cb47d9dfa249cc Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17533 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Jason Lowe-Power <jason@lowepower.com> Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com> Maintainer: Jason Lowe-Power <jason@lowepower.com> Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
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