| Age | Commit message (Collapse) | Author |
|---|
|
Enable the cache to detect contiguous writes and hold on to the MSHR
long enough to allow the entire line to be written. If the whole line
is written, the MSHR will be sent out as an invalidation requests, as
it is part of a whole-line write, i.e. no-fetch-on-write.
The cache is also able to switch to a write-no-allocate policy on the
actual completion of the writes, and instead use the tempBlock and
turn the write operation into a writeback.
These policies are all well-known, and described in works such as
Jouppi, Cache Write Policies and Performance, vol 21, no 2, ACM, 1993.
Change-Id: I19792f2970b3c6798c9b2b493acdd156897284ae
Reviewed-on: https://gem5-review.googlesource.com/c/12907
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
This patch changes how we deal with whole-line writes their
responses. With these changes, we use the MSHR tracking to determine
if a whole-line is written, and on a fill we simply handle the
invalidation response, with the actual writes taking place as part of
satisfying the CPU-side hit.
Change-Id: I9a18e41a95db3c20b97f8bca7d95ff33d35a578b
Reviewed-on: https://gem5-review.googlesource.com/c/12905
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
Rename the files blk.cc and blk.hh to cache_blk.cc and cache_blk.hh
to comply with the usual file-class naming rules.
Change-Id: I8af45df3e4b8dd934fd9929ec914fb230cb2cb09
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/13416
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
"4976ff5 mem-cache: Refactor the recvAtomic function" introduced a bug
where if an atomic request that fills in using the tempBlock it will
not evict it when it finishes handling the request as it should. This
triggers an assertion. This change fixes this bug.
Change-Id: I73c808a7e15237eddb36b5448ef6728f7bcf7fd9
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/12644
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
When a block is being replaced in an allocation, if successfull,
the block will be inserted. Therefore we move the insertion
functionality to allocateBlock().
allocateBlock's signature has been modified to allow this
modification.
Change-Id: I60d17a83ff4f3021fdc976378868ccde6c7507bc
Reviewed-on: https://gem5-review.googlesource.com/10812
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
tempBlock has its member variables manually set in order to allow
it to be used in the block address regeneration function. This is
not necessary, and ti can be simply given the address, so it does
not need to be aware of set and tag. This will simplify
implementation of sector and skewed caches.
Change-Id: Iaffb10c323509722cd5589fe1030b818d43336d6
Reviewed-on: https://gem5-review.googlesource.com/9961
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
This change modifies forEachBlk tags function to accept std::function
as parameter. It also adds an anyBlk tags function that given a
condition, it iterates through the blocks and returns whether the
condition is met.
Finally, it uses forEachBlk to implement the print, computeStats and
cleanupRefs functions that also work for the FALRU class.
Change-Id: I2f75f4baa1fdd5a1d343a63ecace3eb9458fbf03
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10621
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
This patch changes what goes into the BaseCache and what goes into the
Cache, to make it easier to add a NoncoherentCache with as much re-use
as possible. A number of redundant members and definitions are also
removed in the process.
This is a modified version of a changeset put together by Andreas
Hansson <andreas.hansson@arm.com>
Change-Id: Ie9dd73c4ec07732e778e7416b712dad8b4bd5d4b
Reviewed-on: https://gem5-review.googlesource.com/10431
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
Change-Id: I25dbcfcddfe1c422a76eb1af3f726c1360d8d110
Reviewed-on: https://gem5-review.googlesource.com/10426
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
|
|
These files aren't a collection of miscellaneous stuff, they're the
definition of the Logger interface, and a few utility macros for
calling into that interface (panic, warn, etc.).
Change-Id: I84267ac3f45896a83c0ef027f8f19c5e9a5667d1
Reviewed-on: https://gem5-review.googlesource.com/6226
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>
|
|
Change-Id: I6a3a57e3067c247bd6ce6f01ac9459883f4aae2c
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3880
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
NOTE: With this change there is a possibility for `DRAMCtrl::Rank`s
event names to not properly match the rank they were generated by. This
could occur if the public rank member is modified after the Rank's
construction. A patch would mean refactoring Rank and `DRAMCtrl`b to
privatize many of the members of Rank behind getters.
Change-Id: I7b8bd15086f4ffdfd3f40be4aeddac5e786fd78e
Signed-off-by: Sean Wilson <spwilson2@wisc.edu>
Reviewed-on: https://gem5-review.googlesource.com/3745
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
|
|
Change-Id: I0ed4e528cb750a323facdc811dde7f0ed1ff228e
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Andreas Hansson <andreas.hansson@arm.com>
|
|
Previously DPRINTFs printing information about a packet would use ad hoc
formats. This patch changes all DPRINTFs to use the print function
defined by the packet class, making the packet printing format more
uniform and easier to change.
Change-Id: Idd436a9758d4bf70c86a574d524648b2a2580970
Reviewed-by: Andreas Hansson <andreas.hansson@arm.com>
Reviewed-by: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
|
|
If the cache access mode is parallel, i.e. "sequential_access" parameter
is set to "False", tags and data are accessed in parallel. Therefore,
the hit_latency is the maximum latency between tag_latency and
data_latency. On the other hand, if the cache access mode is
sequential, i.e. "sequential_access" parameter is set to "True",
tags and data are accessed sequentially. Therefore, the hit_latency
is the sum of tag_latency plus data_latency.
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
|
|
Change-Id: I6d1feb164a958dde0da87a1cd2698096112c4a82
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
|
|
Prune cache stats that are never actually used.
|
|
Added stat to the cache to account for HardPF'ed blocks that are evicted
before being referenced (over-prefetching).
|
|
This patch breaks out the cache write buffer into a separate class,
without affecting any stats. The goal of the patch is to avoid
encumbering the much-simpler write queue with the complex MSHR
handling. In a follow on patch this simplification allows us to
implement write combining.
The WriteQueue gets its own class, but shares a common ancestor, the
generic Queue, with the MSHRQueue.
|
|
This patch changes how the cache determines if snoops should be
forwarded from the memory side to the CPU side. Instead of having a
parameter, the cache now looks at the port connected on the CPU side,
and if it is a snooping port, then snoops are forwarded. Less error
prone, and less parameters to worry about.
The patch also tidies up the CPU classes to ensure that their I-side
port is not snooping by removing overrides to the snoop request
handler, such that snoop requests will panic via the default
MasterPort implement
|
|
This patch changes the name of a bunch of packet flags and MSHR member
functions and variables to make the coherency protocol easier to
understand. In addition the patch adds and updates lots of
descriptions, explicitly spelling out assumptions.
The following name changes are made:
* the packet memInhibit flag is renamed to cacheResponding
* the packet sharedAsserted flag is renamed to hasSharers
* the packet NeedsExclusive attribute is renamed to NeedsWritable
* the packet isSupplyExclusive is renamed responderHadWritable
* the MSHR pendingDirty is renamed to pendingModified
The cache states, Modified, Owned, Exclusive, Shared are also called
out in the cache and MSHR code to make it easier to understand.
|
|
This patch adds the necessary commands and cache functionality to
allow clean writebacks. This functionality is crucial, especially when
having exclusive (victim) caches. For example, if read-only L1
instruction caches are not sending clean writebacks, there will never
be any spills from the L1 to the L2. At the moment the cache model
defaults to not sending clean writebacks, and this should possibly be
re-evaluated.
The implementation of clean writebacks relies on a new packet command
WritebackClean, which acts much like a Writeback (renamed
WritebackDirty), and also much like a CleanEvict. On eviction of a
clean block the cache either sends a clean evict, or a clean
writeback, and if any copies are still cached upstream the clean
evict/writeback is dropped. Similarly, if a clean evict/writeback
reaches a cache where there are outstanding MSHRs for the block, the
packet is dropped. In the typical case though, the clean writeback
allocates a block in the downstream cache, and marks it writable if
the evicted block was writable.
The patch changes the O3_ARM_v7a L1 cache configuration and the
default L1 caches in config/common/Caches.py
|
|
This patch adds a parameter to control the cache clusivity, that is if
the cache is mostly inclusive or exclusive. At the moment there is no
intention to support strict policies, and thus the options are: 1)
mostly inclusive, or 2) mostly exclusive.
The choice of policy guides the behaviuor on a cache fill, and a new
helper function, allocOnFill, is created to encapsulate the decision
making process. For the timing mode, the decision is annotated on the
MSHR on sending out the downstream packet, and in atomic we directly
pass the decision to handleFill. We (ab)use the tempBlock in cases
where we are not allocating on fill, leaving the rest of the cache
unaffected. Simple and effective.
This patch also makes it more explicit that multiple caches are
allowed to consider a block writable (this is the case
also before this patch). That is, for a mostly inclusive cache,
multiple caches upstream may also consider the block exclusive. The
caches considering the block writable/exclusive all appear along the
same path to memory, and from a coherency protocol point of view it
works due to the fact that we always snoop upwards in zero time before
querying any downstream cache.
Note that this patch does not introduce clean writebacks. Thus, for
clean lines we are essentially removing a cache level if it is made
mostly exclusive. For example, lines from the read-only L1 instruction
cache or table-walker cache are always clean, and simply get dropped
rather than being passed to the L2. If the L2 is mostly exclusive and
does not allocate on fill it will thus never hold the line. A follow
on patch adds the clean writebacks.
The patch changes the L2 of the O3_ARM_v7a CPU configuration to be
mostly exclusive (and stats are affected accordingly).
|
|
This patch changes the CleanEvict command type to not be considered a
write. Initially it was made a zero-sized write to match the writeback
command, but as things developed it became clear that it causes more
problems than it solves. For example, the memory modules (and bridge)
should not consider the CleanEvict as a write, but instead discard
it. With this patch it will be neither a read, nor write, and as it
does not need a response the slave will simply sink it.
|
|
Open up for other subclasses to BaseCache and transition to using the
explicit Cache subclass.
--HG--
rename : src/mem/cache/BaseCache.py => src/mem/cache/Cache.py
|
|
There is no longer any need to keep the implementation in a header.
|
|
This patch removes the RequestCause, and also simplifies how we
schedule the sending of packets through the memory-side port. The
deassertion of bus requests is removed as it is not used.
|
|
Draining is currently done by traversing the SimObject graph and
calling drain()/drainResume() on the SimObjects. This is not ideal
when non-SimObjects (e.g., ports) need draining since this means that
SimObjects owning those objects need to be aware of this.
This changeset moves the responsibility for finding objects that need
draining from SimObjects and the Python-side of the simulator to the
DrainManager. The DrainManager now maintains a set of all objects that
need draining. To reduce the overhead in classes owning non-SimObjects
that need draining, objects inheriting from Drainable now
automatically register with the DrainManager. If such an object is
destroyed, it is automatically unregistered. This means that drain()
and drainResume() should never be called directly on a Drainable
object.
While implementing the new functionality, the DrainManager has now
been made thread safe. In practice, this means that it takes a lock
whenever it manipulates the set of Drainable objects since SimObjects
in different threads may create Drainable objects
dynamically. Similarly, the drain counter is now an atomic_uint, which
ensures that it is manipulated correctly when objects signal that they
are done draining.
A nice side effect of these changes is that it makes the drain state
changes stricter, which the simulation scripts can exploit to avoid
redundant drains.
|
|
This patch takes the final step in removing the is_top_level parameter
from the cache. With the recent changes to read requests and write
invalidations, the parameter is no longer needed, and consequently
removed.
This also means that asymmetric cache hierarchies are now fully
supported (and we are actually using them already with L1 caches, but
no table-walker caches, connected to a shared L2).
|
|
This patch adds a parameter to the BaseCache to enable a read-only
cache, for example for the instruction cache, or table-walker cache
(not for x86). A number of checks are put in place in the code to
ensure a read-only cache does not end up with dirty data.
A follow-on patch adds suitable read requests to allow a read-only
cache to explicitly ask for clean data.
|
|
This patch takes a last step in fixing issues related to uncacheable
accesses. We do not separate uncacheable memory from uncacheable
devices, and in cases where it is really memory, there are valid
scenarios where we need to snoop since we do not support cache
maintenance instructions (yet). On snooping an uncacheable access we
thus provide data if possible. In essence this makes uncacheable
accesses IO coherent.
The snoop filter is also queried to steer the snoops, but not updated
since the uncacheable accesses do not allocate a block.
|
|
This patch removes the no-longer-needed
allocateUncachedReadBuffer. Besides the checks it is exactly the same
as allocateMissBuffer and thus provides no value.
|
|
This patch aligns all MSHR queue entries to block boundaries to
simplify checks for matches. Previously there were corner cases that
could lead to existing entries not being identified as matches.
There are, rather alarmingly, a few regressions that change with this
patch.
|
|
Avoid redundant inclusion of the name in the DPRINTF string.
|
|
This patch fixes a long-standing isue with the port flow
control. Before this patch the retry mechanism was shared between all
different packet classes. As a result, a snoop response could get
stuck behind a request waiting for a retry, even if the send/recv
functions were split. This caused message-dependent deadlocks in
stress-test scenarios.
The patch splits the retry into one per packet (message) class. Thus,
sendTimingReq has a corresponding recvReqRetry, sendTimingResp has
recvRespRetry etc. Most of the changes to the code involve simply
clarifying what type of request a specific object was accepting.
The biggest change in functionality is in the cache downstream packet
queue, facing the memory. This queue was shared by requests and snoop
responses, and it is now split into two queues, each with their own
flow control, but the same physical MasterPort. These changes fixes
the previously seen deadlocks.
|
|
This patch adds some much-needed clarity in the specification of the
cache timing. For now, hit_latency and response_latency are kept as
top-level parameters, but the cache itself has a number of local
variables to better map the individual timing variables to different
behaviours (and sub-components).
The introduced variables are:
- lookupLatency: latency of tag lookup, occuring on any access
- forwardLatency: latency that occurs in case of outbound miss
- fillLatency: latency to fill a cache block
We keep the existing responseLatency
The forwardLatency is used by allocateInternalBuffer() for:
- MSHR allocateWriteBuffer (unchached write forwarded to WriteBuffer);
- MSHR allocateMissBuffer (cacheable miss in MSHR queue);
- MSHR allocateUncachedReadBuffer (unchached read allocated in MSHR
queue)
It is our assumption that the time for the above three buffers is the
same. Similarly, for snoop responses passing through the cache we use
forwardLatency.
|
|
This patch adds a bit of clarification around the assumptions made in
the cache when packets are sent out, and dirty responses are
pending. As part of the change, the marking of an MSHR as in service
is simplified slightly, and comments are added to explain what
assumptions are made.
|
|
Prepare for a different implementation following in the next patch
|
|
Support full-block writes directly rather than requiring RMW:
* a cache line is allocated in the cache upon receipt of a
WriteInvalidateReq, not the WriteInvalidateResp.
* only top-level caches allocate the line; the others just pass
the request along and invalidate as necessary.
* to close a timing window between the *Req and the *Resp, a new
metadata bit tracks whether another cache has read a copy of
the new line before the writeback to memory.
|
|
This patch fixes a bug in the cache port where the retry flag was
reset too early, allowing new requests to arrive before the retry was
actually sent, but with the event already scheduled. This caused a
deadlock in the interactions with the O3 LSQ.
The patche fixes the underlying issue by shifting the resetting of the
flag to be done by the event that also calls sendRetry(). The patch
also tidies up the flow control in recvTimingReq and ensures that we
also check if we already have a retry outstanding.
|
|
This patch adds the basic building blocks required to support e.g. ARM
TrustZone by discerning secure and non-secure memory accesses.
|
|
Add some values and methods to the request object to track the translation
and access latency for a request and which level of the cache hierarchy responded
to the request.
|
|
This patch merely adopts a more strict use of const for the cache
member functions and variables, and also moves a large portion of the
member functions from public to protected.
|
|
the cache drainManager is set but never cleared, this is because
the cache itself does not need to be drained and thus never
triggers a signalDrainDone(). because the drainManager variable
is not used properly and does not appear to be necessary it has
been removed with this patch.
|
|
This patch adds support for the following optional drain methods in
the classical memory system's cache model:
memWriteback() - Write back all dirty cache lines to memory using
functional accesses.
memInvalidate() - Invalidate all cache lines. Dirty cache lines
are lost unless a writeback is requested.
Since memWriteback() is called when checkpointing systems, this patch
adds support for checkpointing systems with caches. The serialization
code now checks whether there are any dirty lines in the cache. If
there are dirty lines in the cache, the checkpoint is flagged as bad
and a warning is printed.
|
|
This patch moves the draining interface from SimObject to a separate
class that can be used by any object needing draining. However,
objects not visible to the Python code (i.e., objects not deriving
from SimObject) still depend on their parents informing them when to
drain. This patch also gets rid of the CountedDrainEvent (which isn't
really an event) and replaces it with a DrainManager.
|
|
This patch adds an additional level of ports in the inheritance
hierarchy, separating out the protocol-specific and protocl-agnostic
parts. All the functionality related to the binding of ports is now
confined to use BaseMaster/BaseSlavePorts, and all the
protocol-specific parts stay in the Master/SlavePort. In the future it
will be possible to add other protocol-specific implementations.
The functions used in the binding of ports, i.e. getMaster/SlavePort
now use the base classes, and the index parameter is updated to use
the PortID typedef with the symbolic InvalidPortID as the default.
|
|
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.
|
|
In the current caches the hit latency is paid twice on a miss. This patch lets
a configurable response latency be set of the cache for the backward path.
|
|
This patch extends the queued port interfaces with methods for
scheduling the transmission of a timing request/response. The methods
are named similar to the corresponding sendTiming(Snoop)Req/Resp,
replacing the "send" with "sched". As the queues are currently
unbounded, the methods always succeed and hence do not return a value.
This functionality was previously provided in the subclasses by
calling PacketQueue::schedSendTiming with the appropriate
parameters. With this change, there is no need to introduce these
extra methods in the subclasses, and the use of the queued interface
is more uniform and explicit.
|
