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This patch optimises the passing of StaticInstPtr by avoiding copying
the reference-counting pointer. This avoids first incrementing and
then decrementing the reference-counting pointer.
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The call paths for de-scheduling a thread are halt() and suspend(), from
the thread context. There is no call to deallocateContext() in general,
though some CPUs chose to define it. This patch removes the function
from BaseCPU and the cores which do not require it.
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activate(), suspend(), and halt() used on thread contexts had an optional
delay parameter. However this parameter was often ignored. Also, when used,
the delay was seemily arbitrarily set to 0 or 1 cycle (no other delays were
ever specified). This patch removes the delay parameter and 'Events'
associated with them across all ISAs and cores. Unused activate logic
is also removed.
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Instead of having code embedded in cpu model to do simpoint profiling use
the probes infrastructure to do it.
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This patch changes how faults are passed between methods in an attempt
to copy as few reference-counting pointer instances as possible. This
should avoid unecessary copies being created, contributing to the
increment/decrement of the reference counters.
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Put the packet type swizzling (that is currently done in a lot of places)
into a refineCommand() member function.
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We currently generate and compile one version of the ISA code per CPU
model. This is obviously wasting a lot of resources at compile
time. This changeset factors out the interface into a separate
ExecContext class, which also serves as documentation for the
interface between CPUs and the ISA code. While doing so, this
changeset also fixes up interface inconsistencies between the
different CPU models.
The main argument for using one set of ISA code per CPU model has
always been performance as this avoid indirect branches in the
generated code. However, this argument does not hold water. Booting
Linux on a simulated ARM system running in atomic mode
(opt/10.linux-boot/realview-simple-atomic) is actually 2% faster
(compiled using clang 3.4) after applying this patch. Additionally,
compilation time is decreased by 35%.
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For the o3, add instruction mix (OpClass) histogram at commit (stats
also already collected at issue). For the simple CPUs we add a
histogram of executed instructions
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This changesets adds branch predictor support to the
BaseSimpleCPU. The simple CPUs normally don't need a branch predictor,
however, there are at least two cases where it can be desirable:
1) A simple CPU can be used to warm the branch predictor of an O3
CPU before switching to the slower O3 model.
2) The simple CPU can be used as a quick way of evaluating/debugging
new branch predictors since it exposes branch predictor
statistics.
Limitations:
* Since the simple CPU doesn't speculate, only one instruction will
be active in the branch predictor at a time (i.e., the branch
predictor will never see speculative branches).
* The outcome of a branch prediction does not affect the performance
of the simple CPU.
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snooped.
This patch add support for generating wake-up events in the CPU when an address
that is currently in the exclusive state is hit by a snoop. This mechanism is required
for ARMv8 multi-processor support.
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This patch enables tracking of cache occupancy per thread along with
ages (in buckets) per cache blocks. Cache occupancy stats are
recalculated on each stat dump.
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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.
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This patch removes an assertion in the simpoint profiling code that
asserts that a previously-seen basic block has the exact same number
of instructions executed as before. This can be false if the basic
block generates aborts or takes interrupts at different locations
within the basic block. The basic block profiling are not affected
significantly as these events are rare in general.
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Add a third register class for condition codes,
in parallel with the integer and FP classes.
No ISAs use the CC class at this point though.
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Make these names more meaningful.
Specifically, made these substitutions:
s/FP_Base_DepTag/FP_Reg_Base/g;
s/Ctrl_Base_DepTag/Misc_Reg_Base/g;
s/Max_DepTag/Max_Reg_Index/g;
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This patch fixes up the comment formatting for isDrained in the timing
CPU.
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Added a couple missing updates to the notIdleFraction stat. Without
these, it sometimes gives a (not) idle fraction that is greater than 1
or less than 0.
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This patch modifies the SimpleTimingCPU drain check to also consider
the fetch event. Previously, there was an assumption that there is
never a fetch event scheduled if the CPU is not executing
microcode. However, when a context is activated, a fetch even is
scheduled, and microPC() is zero.
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This patch removes the notion of a peer block size and instead sets
the cache line size on the system level.
Previously the size was set per cache, and communicated through the
interconnect. There were plenty checks to ensure that everyone had the
same size specified, and these checks are now removed. Another benefit
that is not yet harnessed is that the cache line size is now known at
construction time, rather than after the port binding. Hence, the
block size can be locally stored and does not have to be queried every
time it is used.
A follow-on patch updates the configuration scripts accordingly.
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This patch changes the type of the hash function for BasicBlockRanges
to match the original definition of the templatized type. Without
this, clang raises a warning and combined with the "-Werror" flag this
causes compilation to fail.
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Previously, nextCycle() could return the *current* cycle if the current tick was
already aligned with the clock edge. This behavior is not only confusing (not
quite what the function name implies), but also caused problems in the
drainResume() function. When exiting/re-entering the sim loop (e.g., to take
checkpoints), the CPUs will drain and resume. Due to the previous behavior of
nextCycle(), the CPU tick events were being rescheduled in the same ticks that
were already processed before draining. This caused divergence from runs that
did not exit/re-entered the sim loop. (Initially a cycle difference, but a
significant impact later on.)
This patch separates out the two behaviors (nextCycle() and clockEdge()),
uses nextCycle() in drainResume, and uses clockEdge() everywhere else.
Nothing (other than name) should change except for the drainResume timing.
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This patch is based on http://reviews.m5sim.org/r/1474/ originally written by
Mitch Hayenga. Basic block vectors are generated (simpoint.bb.gz in simout
folder) based on start and end addresses of basic blocks.
Some comments to the original patch are addressed and hooks are added to create
and resume from checkpoints based on instruction counts dictated by external
SimPoint analysis tools.
SimPoint creation/resuming options will be implemented as a separate patch.
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This patch changes the port in the CPU classes to use MasterPort
instead of the derived CpuPort. The functions of the CpuPort are now
distributed across the relevant subclasses. The port accessor
functions (getInstPort and getDataPort) now return a MasterPort
instead of a CpuPort. This simplifies creating derivative CPUs that do
not use the CpuPort.
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Virtualized CPUs and the fastmem mode of the atomic CPU require direct
access to physical memory. We currently require caches to be disabled
when using them to prevent chaos. This is not ideal when switching
between hardware virutalized CPUs and other CPU models as it would
require a configuration change on each switch. This changeset
introduces a new version of the atomic memory mode,
'atomic_noncaching', where memory accesses are inserted into the
memory system as atomic accesses, but bypass caches.
To make memory mode tests cleaner, the following methods are added to
the System class:
* isAtomicMode() -- True if the memory mode is 'atomic' or 'direct'.
* isTimingMode() -- True if the memory mode is 'timing'.
* bypassCaches() -- True if caches should be bypassed.
The old getMemoryMode() and setMemoryMode() methods should never be
used from the C++ world anymore.
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CPUs need to test that the memory system is in the right mode in two
places, when the CPU is initialized (unless it's switched out) and on
a drainResume(). This led to some code duplication in the CPU
models. This changeset introduces the verifyMemoryMode() method which
is called by BaseCPU::init() if the CPU isn't switched out. The
individual CPU models are responsible for calling this method when
resuming from a drain as this code is CPU model specific.
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The configuration scripts currently hard-code the requirements of each
CPU. This is clearly not optimal as it makes writing new configuration
scripts painful and adding new CPU models requires existing scripts to
be updated. This patch adds the following class methods to the base
CPU and all relevant CPUs:
* memory_mode -- Return a string describing the current memory mode
(invalid/atomic/timing).
* require_caches -- Does the CPU model require caches?
* support_take_over -- Does the CPU support CPU handover?
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The changes made by the changeset 9376 were not quite correct. The patch made
changes to the code which resulted in decoder not getting initialized correctly
when the state was restored from a checkpoint.
This patch adds a startup function to each ISA object. For x86, this function
sets the required state in the decoder. For other ISAs, the function is empty
right now.
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Cleanup the serialization code for the simple CPUs and the O3 CPU. The
CPU-specific code has been replaced with a (un)serializeThread that
serializes the thread state / context of a specific thread. Assuming
that the thread state class uses the CPU-specific thread state uses
the base thread state serialization code, this allows us to restore a
checkpoint with any of the CPU models.
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Currently, the atomic CPU can be in the middle of a microcode sequence
when it is drained. This leads to two problems:
* When switching to a hardware virtualized CPU, we obviously can't
execute gem5 microcode.
* Since curMacroStaticInst is populated when executing microcode,
repeated switching between CPUs executing microcode leads to
incorrect execution.
After applying this patch, the CPU will be on a proper instruction
boundary, which means that it is safe to switch to any CPU model
(including hardware virtualized ones). This changeset fixes a bug
where the multiple switches to the same atomic CPU sometimes corrupts
the target state because of dangling pointers to the currently
executing microinstruction.
Note: This changeset moves tick event descheduling from switchOut() to
drain(), which makes timing consistent between just draining a system
and draining /and/ switching between two atomic CPUs. This makes
debugging quite a lot easier (execution traces get the same timing),
but the latency of the last instruction before a drain will not be
accounted for correctly (it will always be 1 cycle).
Note 2: This changeset removes so_state variable, the locked variable,
and the tickEvent from checkpoints since none of them contain state
that needs to be preserved across checkpoints. The so_state is made
redundant because we don't use the drain state variable anymore, the
lock variable should never be set when the system is drained, and the
tick event isn't scheduled.
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Currently, the timing CPU can be in the middle of a microcode sequence
or multicycle (stayAtPC is true) instruction when it is drained. This
leads to two problems:
* When switching to a hardware virtualized CPU, we obviously can't
execute gem5 microcode.
* If stayAtPC is true we might execute half of an instruction twice
when restoring a checkpoint or switching CPUs, which leads to an
incorrect execution.
After applying this patch, the CPU will be on a proper instruction
boundary, which means that it is safe to switch to any CPU model
(including hardware virtualized ones). This changeset also fixes a bug
where the timing CPU sometimes switches out with while stayAtPC is
true, which corrupts the target state after a CPU switch or
checkpoint.
Note: This changeset removes the so_state variable from checkpoints
since the drain state isn't used anymore.
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The defer_registration parameter is used to prevent a CPU from
initializing at startup, leaving it in the "switched out" mode. The
name of this parameter (and the help string) is confusing. This patch
renames it to switched_out, which should be more descriptive.
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This patch cleans up the CPU switching functionality by making sure
that CPU models consistently call the parent on switchOut() and
takeOverFrom(). This has the following implications that might alter
current functionality:
* The call to BaseCPU::switchout() in the O3 CPU is moved from
signalDrained() (!) to switchOut().
* A call to BaseSimpleCPU::switchOut() is introduced in the simple
CPUs.
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This patch adds checks to all CPU models to make sure that the memory
system is in the correct mode at startup and when resuming after a
drain. Previously, we only checked that the memory system was in the
right mode when resuming. This is inadequate since this is a
configuration error that should be detected at startup as well as when
resuming. Additionally, since the check was done using an assert, it
wasn't performed when NDEBUG was set (e.g., the fast target).
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The ISA class on stores the contents of ID registers on many
architectures. In order to make reset values of such registers
configurable, we make the class inherit from SimObject, which allows
us to use the normal generated parameter headers.
This patch introduces a Python helper method, BaseCPU.createThreads(),
which creates a set of ISAs for each of the threads in an SMT
system. Although it is currently only needed when creating
multi-threaded CPUs, it should always be called before instantiating
the system as this is an obvious place to configure ID registers
identifying a thread/CPU.
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This interface is no longer used, and getting rid of it simplifies the
decoders and code that sets up the decoders. The thread context had been used
to read architectural state which was used to contextualize the instruction
memory as it came in. That was changed so that the state is now sent to the
decoders to keep locally if/when it changes. That's significantly more
efficient.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
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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.
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When casting objects in the generated SWIG interfaces, SWIG uses
classical C-style casts ( (Foo *)bar; ). In some cases, this can
degenerate into the equivalent of a reinterpret_cast (mainly if only a
forward declaration of the type is available). This usually works for
most compilers, but it is known to break if multiple inheritance is
used anywhere in the object hierarchy.
This patch introduces the cxx_header attribute to Python SimObject
definitions, which should be used to specify a header to include in
the SWIG interface. The header should include the declaration of the
wrapped object. We currently don't enforce header the use of the
header attribute, but a warning will be generated for objects that do
not use it.
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This patch takes the final plunge and transitions from the templated
Range class to the more specific AddrRange. In doing so it changes the
obvious Range<Addr> to AddrRange, and also bumps the range_map to be
AddrRangeMap.
In addition to the obvious changes, including the removal of redundant
includes, this patch also does some house keeping in preparing for the
introduction of address interleaving support in the ranges. The Range
class is also stripped of all the functionality that is never used.
--HG--
rename : src/base/range.hh => src/base/addr_range.hh
rename : src/base/range_map.hh => src/base/addr_range_map.hh
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This patch addresses the comments and feedback on the preceding patch
that reworks the clocks and now more clearly shows where cycles
(relative cycle counts) are used to express time.
Instead of bumping the existing patch I chose to make this a separate
patch, merely to try and focus the discussion around a smaller set of
changes. The two patches will be pushed together though.
This changes done as part of this patch are mostly following directly
from the introduction of the wrapper class, and change enough code to
make things compile and run again. There are definitely more places
where int/uint/Tick is still used to represent cycles, and it will
take some time to chase them all down. Similarly, a lot of parameters
should be changed from Param.Tick and Param.Unsigned to
Param.Cycles.
In addition, the use of curTick is questionable as there should not be
an absolute cycle. Potential solutions can be built on top of this
patch. There is a similar situation in the o3 CPU where
lastRunningCycle is currently counting in Cycles, and is still an
absolute time. More discussion to be had in other words.
An additional change that would be appropriate in the future is to
perform a similar wrapping of Tick and probably also introduce a
Ticks class along with suitable operators for all these classes.
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This patch introduces the notion of a clock update function that aims
to avoid costly divisions when turning the current tick into a
cycle. Each clocked object advances a private (hidden) cycle member
and a tick member and uses these to implement functions for getting
the tick of the next cycle, or the tick of a cycle some time in the
future.
In the different modules using the clocks, changes are made to avoid
counting in ticks only to later translate to cycles. There are a few
oddities in how the O3 and inorder CPU count idle cycles, as seen by a
few locations where a cycle is subtracted in the calculation. This is
done such that the regression does not change any stats, but should be
revisited in a future patch.
Another, much needed, change that is not done as part of this patch is
to introduce a new typedef uint64_t Cycle to be able to at least hint
at the unit of the variables counting Ticks vs Cycles. This will be
done as a follow-up patch.
As an additional follow up, the thread context still uses ticks for
the book keeping of last activate and last suspend and this should
probably also be changed into cycles as well.
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This patch removes the NACK frrom the packet as there is no longer any
module in the system that issues them (the bridge was the only one and
the previous patch removes that).
The handling of NACKs was mostly avoided throughout the code base, by
using e.g. panic or assert false, but in a few locations the NACKs
were actually dealt with (although NACKs never occured in any of the
regressions). Most notably, the DMA port will now never receive a NACK
and the backoff time is thus never changed. As a consequence, the
entire backoff mechanism (similar to a PCI bus) is now removed and the
DMA port entirely relies on the bus performing the arbitration and
issuing a retry when appropriate. This is more in line with e.g. PCIe.
Surprisingly, this patch has no impact on any of the regressions. As
mentioned in the patch that removes the NACK from the bridge, a
follow-up patch should change the request and response buffer size for
at least one regression to also verify that the system behaves as
expected when the bridge fills up.
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DPRINTFs
This patch fixes some problems with the drain/switchout functionality
for the O3 cpu and for the ARM ISA and adds some useful debug print
statements.
This is an incremental fix as there are still a few bugs/mem leaks with the
switchout code. Particularly when switching from an O3CPU to a
TimingSimpleCPU. However, when switching from O3 to O3 cores with the ARM ISA
I haven't encountered any more assertion failures; now the kernel will
typically panic inside of simulation.
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This patch is a first step to align the port names used in the Python
world and the C++ world. Ultimately it serves to make the use of
config.json together with output from the simulation easier, including
post-processing of statistics.
Most notably, the CPU, cache, and bus is addressed in this patch, and
there might be other ports that should be updated accordingly. The
dash name separator has also been replaced with a "." which is what is
used to concatenate the names in python, and a separation is made
between the master and slave port in the bus.
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This patch is the last part of moving all protocol-related
functionality out of the Port base class. All the send/recv functions
are already moved, and the retry (which still governs all the timing
transport functions) is the only part that remained in the base class.
The only point where this currently causes a bit of inconvenience is
in the bus where the retry list is global and holds Port pointers (not
Master/SlavePort). This is about to change with the split into a
request/response bus and will soon be removed anyway.
The patch has no impact on any regressions.
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This patch is trivial and merely prunes a pointer that was never set
or used.
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initCPU() will be called to initialize switched out CPUs for the simple and
inorder CPU models. this patch prevents those CPUs from being initialized
because they should get their state from the active CPU when it is switched
out.
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These classes are always used together, and merging them will give the ISAs
more flexibility in how they cache things and manage the process.
--HG--
rename : src/arch/x86/predecoder_tables.cc => src/arch/x86/decoder_tables.cc
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