The create() method on Params structs usually instantiate SimObjects
using a constructor which takes the Params struct as a parameter
somehow. There has been a lot of needless variation in how that was
done, making it annoying to pass Params down to base classes. Some of
the different forms were:
const Params &
Params &
Params *
const Params *
Params const*
This change goes through and fixes up every constructor and every
create() method to use the const Params & form. We use a reference
because the Params struct should never be null. We use const because
neither the create method nor the consuming object should modify the
record of the parameters as they came in from the config. That would
make consuming them not idempotent, and make it impossible to tell what
the actual simulation configuration was since it would change from any
user visible form (config script, config.ini, dot pdf output).
Change-Id: I77453cba52fdcfd5f4eec92dfb0bddb5a9945f31
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35938
Reviewed-by: Gabe Black <gabeblack@google.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Allow all sub-compressors of BDI to be successful as long as
they are able to compress. Then, BDI's actual size threshold
acts as the cutting point.
This situation arises on any multi compressor; yet, generalizing
this assumption might be too bold.
Change-Id: Iec5057d16d4a7ba5fb573133a30ea10869bd67e0
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33386
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The size can be zero in special occasions, which would
generate divisions by zero. This patch expands the
stats to support them. It also fixes the compression
factor calculation in the Multi compressor.
As a side effect, now that zero sizes are handled, allow
the Zero compressor to generate it.
Change-Id: I9f7dee76576b09fdc9bef3e1f3f89be3726dcbd9
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33383
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
When compressing using a multi-compressor, one must be able to
identify which sub-compressor should be used to decompress data.
This can be achieved by either adding encoding bits to block's
tag or data entry.
It was previously assumed that these encoding bits would be added
to the tag, but now make it a parameter that defaults to the data
entry.
Change-Id: Id322425e7a6ad59cb2ec7a4167a43de4c55c482c
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33380
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The compressors are not able to process a whole line at once,
so they must divide it into multiple same-sized chunks. This
patch makes the base compressor responsible for this division,
so that the derived classes are mostly agnostic to this
translation.
This change has been coupled with a change of the signature
of the public compress() to avoid introducing a temporary
function rename. Previously, this function did not return
the compressed data, under the assumption that everything
related to the compressed data would be handled by the
compressor. However, sometimes the units using the compressor
could need to know or store the compressed data.
For example, when sharing dictionaries the compressed data
must be checked to determine if two blocks can co-allocate
(DISH, Panda et al. 2016).
Change-Id: Id8dbf68936b1457ca8292cc0a852b0f0a2eeeb51
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33379
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Previously either the compression data was the one declared within
DictionaryCompressor, or the derived class would have to override
the compress() to use a derived compression data.
With this change, the instantiation can be overridden, and thus
any derived class can choose the compression data pointer type
they need to use.
Change-Id: I387936265a3de6785a6096c7a6bd21774202b1c7
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33378
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
When applying the bitwise not to a short integer the compiler
automatically promotes it to an integer. For example, if a 8-bit
mask=0xFF, and the compiler decides to promote the mask to 32-bit
to apply the bitwise not, ~mask=0xFFFFFF00, which will yield wrong
results for popcount(): expected=0, got=24.
Change-Id: I95efba5532c27ca004ff6947d4b51a8a14f09741
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33374
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Creation of the Compressor namespace. It encapsulates all the cache
compressors, and other classes used by them.
The following classes have been renamed:
BaseCacheCompressor -> Base
PerfectCompressor - Perfect
RepeatedQwordsCompressor -> RepeatedQwords
ZeroCompressor -> Zero
BaseDictionaryCompressor and DictionaryCompressor were not renamed
because the there is a high probability that users may want to
create a Dictionary class that encompasses the dictionary contained
by these compressors.
To apply this patch one must force recompilation (e.g., by deleting
it) of build/<arch>/params/BaseCache.hh (and any other files that
were previously using these compressors).
Change-Id: I78cb3b6fb8e3e50a52a04268e0e08dd664d81230
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33294
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The priority queue comparator orders such that false gives the
entry a higher priority. Therefore, if it is desired to make
the entry with lowest decompression latency have higher priority,
the comparison must be inverted.
Can be tested with:
MultiCompressor(compressors=[
PerfectCompressor(decompression_latency=1),
PerfectCompressor(decompression_latency=2)])
Where it is expected that compressor0 (the one with decomp lat
of 1) is always chosen.
Change-Id: I44acbf5f51c6e47efdd2a16fba9596935cf2eb69
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28367
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
The type of the local unique_ptr variable was different from the return type.
In C++11 because of such difference, a copy-ellision would not be possible,
and that required the use of a std::move.
In C++14 the restriction of same types being required was removed, so
std::move would not be needed anymore.
With the addition of the -Wredundant-move warning in newer compilers, having
the std::move on the return became an issue, breaking compilation.
Change-Id: I45d18dfc500bb5db5fe360814feb91853c735a19
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22403
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
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>
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>
