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author | Daniel R. Carvalho <odanrc@yahoo.com.br> | 2018-02-19 15:13:11 +0100 |
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committer | Daniel Carvalho <odanrc@yahoo.com.br> | 2018-03-22 14:50:23 +0000 |
commit | d207e9ccee411877fdeac80bb68a27900560f50f (patch) | |
tree | 120810cf72c52ed5df29436552e06f1fb11aa5ce /src/mem/cache/blk.hh | |
parent | 0473286ab1e9992a906eff380000bf90c82eeccb (diff) | |
download | gem5-d207e9ccee411877fdeac80bb68a27900560f50f.tar.xz |
mem-cache: Split array indexing and replacement policies.
Replacement policies (LRU, Random) are currently considered as array
indexing methods, but have completely different functionalities:
- Array indexers determine the possible locations for block allocation.
This information is used to generate replacement candidates when
conflicts happen.
- Replacement policies determine which of the replacement candidates
should be evicted to make room for new allocations.
For this reason, they were split into different classes. Advantages:
- Easier and more straightforward to implement other replacement
policies (RRIP, LFU, ARC, ...)
- Allow easier future implementation of cache organization schemes
As now we can't assure the use of sets, the previous way to create a
true LRU is not viable. Now a timestamp_bits parameter controls how
many bits are dedicated for the timestamp, and a true LRU can be
achieved through an infinite number of bits (although a few bits suffice
in practice).
Change-Id: I23750db121f1474d17831137e6ff618beb2b3eda
Reviewed-on: https://gem5-review.googlesource.com/8501
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Diffstat (limited to 'src/mem/cache/blk.hh')
-rw-r--r-- | src/mem/cache/blk.hh | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/src/mem/cache/blk.hh b/src/mem/cache/blk.hh index 7dd0a92ae..a1e45028b 100644 --- a/src/mem/cache/blk.hh +++ b/src/mem/cache/blk.hh @@ -99,7 +99,7 @@ class CacheBlk /** The current status of this block. @sa CacheBlockStatusBits */ State status; - /** Which curTick() will this block be accessable */ + /** Which curTick() will this block be accessible */ Tick whenReady; /** @@ -108,7 +108,10 @@ class CacheBlk */ int set, way; - /** whether this block has been touched */ + /** + * Whether this block has been touched since simulation started. + * Used to calculate number of used tags. + */ bool isTouched; /** Number of references to this block since it was brought in. */ @@ -117,8 +120,15 @@ class CacheBlk /** holds the source requestor ID for this block. */ int srcMasterId; + /** Tick on which the block was inserted in the cache. */ Tick tickInserted; + /** + * Replacement policy data. As of now it is only an update timestamp. + * Tick on which the block was last touched. + */ + Tick lastTouchTick; + protected: /** * Represents that the indicated thread context has a "lock" on |