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.
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.
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?
This patch moves the branch predictor files in the o3 and inorder directories
to src/cpu/pred. This allows sharing the branch predictor across different
cpu models.
This patch was originally posted by Timothy Jones in July 2010
but never made it to the repository.
--HG--
rename : src/cpu/o3/bpred_unit.cc => src/cpu/pred/bpred_unit.cc
rename : src/cpu/o3/bpred_unit.hh => src/cpu/pred/bpred_unit.hh
rename : src/cpu/o3/bpred_unit_impl.hh => src/cpu/pred/bpred_unit_impl.hh
rename : src/cpu/o3/sat_counter.hh => src/cpu/pred/sat_counter.hh
The thread context handover code used to break when multiple handovers
were performed during the same quiesce period. Previously, the thread
contexts would assign the TC pointer in the old quiesce event to the
new TC. This obviously broke in cases where multiple switches were
performed within the same quiesce period, in which case the TC pointer
in the quiesce event would point to an old CPU.
The new implementation deschedules pending quiesce events in the old
TC and schedules a new quiesce event in the new TC. The code has been
refactored to remove most of the code duplication.
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.
The O3 CPU used to copy its thread context to a SimpleThread in order
to do serialization. This was a bit of a hack involving two static
SimpleThread instances and a magic constructor that was only used by
the O3 CPU.
This patch moves the ThreadContext serialization code into two global
procedures that, in addition to the normal serialization parameters,
take a ThreadContext reference as a parameter. This allows us to reuse
the serialization code in all ThreadContext implementations.
Some architectures map registers differently depending on their mode
of operations. There is currently no architecture independent way of
accessing all registers. This patch introduces a flat register
interface to the ThreadContext class. This interface is useful, for
example, when serializing or copying thread contexts.
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).
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.
isSyscall was originally created because during handling of a syscall in SE
mode the threadcontext had to be updated. However, in many places this is used
in FS mode (e.g. fault handlers) and the name doesn't make much sense. The
boolean actually stops gem5 from squashing speculative and non-committed state
when a write to a threadcontext happens, so re-name the variable to something
more appropriate
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>
globalHistoryBits, globalPredictorSize, and choicePredictorSize are decoupled.
globalHistoryBits controls how much history is kept, global and choice
predictor sizes control how much of that history is used when accessing
predictor tables. This way, global and choice predictors can actually be
different sizes, and it is no longer possible to walk off the predictor arrays
and cause a seg fault.
There are now individual thresholds for choice, global, and local saturating
counters, so that taken/not taken decisions are correct even when the
predictors' counters' sizes are different.
The interface for localPredictorSize has been removed from TournamentBP because
the value can be calculated from localHistoryBits.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
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.
This patch is a first step to using Cycles as a parameter type. The
main affected modules are the CPUs and the Ruby caches. There are
definitely plenty more places that are affected, but this patch serves
as a starting point to making the transition.
An important part of this patch is to actually enable parameters to be
specified as Param.Cycles which involves some changes to params.py.
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.
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.
This patch removes the overloading of the parameter, which seems both
redundant, and possibly incorrect.
The inorder CPU is particularly interesting as it uses a different
name for the parameter, and never make any use of it internally.
This replaces a (potentially uninitialized) string
field with a virtual function so that we can have
a safe interface without requiring changes to the
eio code.
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.
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.
While FastAlloc provides a small performance increase (~1.5%) over regular malloc it isn't thread safe.
After removing FastAlloc and using tcmalloc I've seen a performance increase of 12% over libc malloc
when running twolf for ARM.
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
This patch moves send/recvTiming and send/recvTimingSnoop from the
Port base class to the MasterPort and SlavePort, and also splits them
into separate member functions for requests and responses:
send/recvTimingReq, send/recvTimingResp, and send/recvTimingSnoopReq,
send/recvTimingSnoopResp. A master port sends requests and receives
responses, and also receives snoop requests and sends snoop
responses. A slave port has the reciprocal behaviour as it receives
requests and sends responses, and sends snoop requests and receives
snoop responses.
For all MemObjects that have only master ports or slave ports (but not
both), e.g. a CPU, or a PIO device, this patch merely adds more
clarity to what kind of access is taking place. For example, a CPU
port used to call sendTiming, and will now call
sendTimingReq. Similarly, a response previously came back through
recvTiming, which is now recvTimingResp. For the modules that have
both master and slave ports, e.g. the bus, the behaviour was
previously relying on branches based on pkt->isRequest(), and this is
now replaced with a direct call to the apprioriate member function
depending on the type of access. Please note that send/recvRetry is
still shared by all the timing accessors and remains in the Port base
class for now (to maintain the current bus functionality and avoid
changing the statistics of all regressions).
The packet queue is split into a MasterPort and SlavePort version to
facilitate the use of the new timing accessors. All uses of the
PacketQueue are updated accordingly.
With this patch, the type of packet (request or response) is now well
defined for each type of access, and asserts on pkt->isRequest() and
pkt->isResponse() are now moved to the appropriate send member
functions. It is also worth noting that sendTimingSnoopReq no longer
returns a boolean, as the semantics do not alow snoop requests to be
rejected or stalled. All these assumptions are now excplicitly part of
the port interface itself.
This patch simplifies the packet by removing the broadcast flag and
instead more firmly relying on (and enforcing) the semantics of
transactions in the classic memory system, i.e. request packets are
routed from a master to a slave based on the address, and when they
are created they have neither a valid source, nor destination. On
their way to the slave, the request packet is updated with a source
field for all modules that multiplex packets from multiple master
(e.g. a bus). When a request packet is turned into a response packet
(at the final slave), it moves the potentially populated source field
to the destination field, and the response packet is routed through
any multiplexing components back to the master based on the
destination field.
Modules that connect multiplexing components, such as caches and
bridges store any existing source and destination field in the sender
state as a stack (just as before).
The packet constructor is simplified in that there is no longer a need
to pass the Packet::Broadcast as the destination (this was always the
case for the classic memory system). In the case of Ruby, rather than
using the parameter to the constructor we now rely on setDest, as
there is already another three-argument constructor in the packet
class.
In many places where the packet information was printed as part of
DPRINTFs, request packets would be printed with a numeric "dest" that
would always be -1 (Broadcast) and that field is now removed from the
printing.
This patch introduces port access methods that separates snoop
request/responses from normal memory request/responses. The
differentiation is made for functional, atomic and timing accesses and
builds on the introduction of master and slave ports.
Before the introduction of this patch, the packets belonging to the
different phases of the protocol (request -> [forwarded snoop request
-> snoop response]* -> response) all use the same port access
functions, even though the snoop packets flow in the opposite
direction to the normal packet. That is, a coherent master sends
normal request and receives responses, but receives snoop requests and
sends snoop responses (vice versa for the slave). These two distinct
phases now use different access functions, as described below.
Starting with the functional access, a master sends a request to a
slave through sendFunctional, and the request packet is turned into a
response before the call returns. In a system without cache coherence,
this is all that is needed from the functional interface. For the
cache-coherent scenario, a slave also sends snoop requests to coherent
masters through sendFunctionalSnoop, with responses returned within
the same packet pointer. This is currently used by the bus and caches,
and the LSQ of the O3 CPU. The send/recvFunctional and
send/recvFunctionalSnoop are moved from the Port super class to the
appropriate subclass.
Atomic accesses follow the same flow as functional accesses, with
request being sent from master to slave through sendAtomic. In the
case of cache-coherent ports, a slave can send snoop requests to a
master through sendAtomicSnoop. Just as for the functional access
methods, the atomic send and receive member functions are moved to the
appropriate subclasses.
The timing access methods are different from the functional and atomic
in that requests and responses are separated in time and
send/recvTiming are used for both directions. Hence, a master uses
sendTiming to send a request to a slave, and a slave uses sendTiming
to send a response back to a master, at a later point in time. Snoop
requests and responses travel in the opposite direction, similar to
what happens in functional and atomic accesses. With the introduction
of this patch, it is possible to determine the direction of packets in
the bus, and no longer necessary to look for both a master and a slave
port with the requested port id.
In contrast to the normal recvFunctional, recvAtomic and recvTiming
that are pure virtual functions, the recvFunctionalSnoop,
recvAtomicSnoop and recvTimingSnoop have a default implementation that
calls panic. This is to allow non-coherent master and slave ports to
not implement these functions.
This patch addresses a number of minor issues that cause problems when
compiling with clang >= 3.0 and gcc >= 4.6. Most importantly, it
avoids using the deprecated ext/hash_map and instead uses
unordered_map (and similarly so for the hash_set). To make use of the
new STL containers, g++ and clang has to be invoked with "-std=c++0x",
and this is now added for all gcc versions >= 4.6, and for clang >=
3.0. For gcc >= 4.3 and <= 4.5 and clang <= 3.0 we use the tr1
unordered_map to avoid the deprecation warning.
The addition of c++0x in turn causes a few problems, as the
compiler is more stringent and adds a number of new warnings. Below,
the most important issues are enumerated:
1) the use of namespaces is more strict, e.g. for isnan, and all
headers opening the entire namespace std are now fixed.
2) another other issue caused by the more stringent compiler is the
narrowing of the embedded python, which used to be a char array,
and is now unsigned char since there were values larger than 128.
3) a particularly odd issue that arose with the new c++0x behaviour is
found in range.hh, where the operator< causes gcc to complain about
the template type parsing (the "<" is interpreted as the beginning
of a template argument), and the problem seems to be related to the
begin/end members introduced for the range-type iteration, which is
a new feature in c++11.
As a minor update, this patch also fixes the build flags for the clang
debug target that used to be shared with gcc and incorrectly use
"-ggdb".
This patch removes the assumption on having on single instance of
PhysicalMemory, and enables a distributed memory where the individual
memories in the system are each responsible for a single contiguous
address range.
All memories inherit from an AbstractMemory that encompasses the basic
behaviuor of a random access memory, and provides untimed access
methods. What was previously called PhysicalMemory is now
SimpleMemory, and a subclass of AbstractMemory. All future types of
memory controllers should inherit from AbstractMemory.
To enable e.g. the atomic CPU and RubyPort to access the now
distributed memory, the system has a wrapper class, called
PhysicalMemory that is aware of all the memories in the system and
their associated address ranges. This class thus acts as an
infinitely-fast bus and performs address decoding for these "shortcut"
accesses. Each memory can specify that it should not be part of the
global address map (used e.g. by the functional memories by some
testers). Moreover, each memory can be configured to be reported to
the OS configuration table, useful for populating ATAG structures, and
any potential ACPI tables.
Checkpointing support currently assumes that all memories have the
same size and organisation when creating and resuming from the
checkpoint. A future patch will enable a more flexible
re-organisation.
--HG--
rename : src/mem/PhysicalMemory.py => src/mem/AbstractMemory.py
rename : src/mem/PhysicalMemory.py => src/mem/SimpleMemory.py
rename : src/mem/physical.cc => src/mem/abstract_mem.cc
rename : src/mem/physical.hh => src/mem/abstract_mem.hh
rename : src/mem/physical.cc => src/mem/simple_mem.cc
rename : src/mem/physical.hh => src/mem/simple_mem.hh
This patch introduces the notion of a master and slave port in the C++
code, thus bringing the previous classification from the Python
classes into the corresponding simulation objects and memory objects.
The patch enables us to classify behaviours into the two bins and add
assumptions and enfore compliance, also simplifying the two
interfaces. As a starting point, isSnooping is confined to a master
port, and getAddrRanges to slave ports. More of these specilisations
are to come in later patches.
The getPort function is not getMasterPort and getSlavePort, and
returns a port reference rather than a pointer as NULL would never be
a valid return value. The default implementation of these two
functions is placed in MemObject, and calls fatal.
The one drawback with this specific patch is that it requires some
code duplication, e.g. QueuedPort becomes QueuedMasterPort and
QueuedSlavePort, and BusPort becomes BusMasterPort and BusSlavePort
(avoiding multiple inheritance). With the later introduction of the
port interfaces, moving the functionality outside the port itself, a
lot of the duplicated code will disappear again.
This patch unifies where initMemProxies is called, in the init()
method of each BaseCPU subclass, before TheISA::initCPU is
called. Moreover, it also ensures that initMemProxies is called in
both full-system and syscall-emulation mode, thus unifying also across
the modes. An additional check is added in the ThreadState to ensure
that initMemProxies is only called once.
This patch cleans up a number of minor issues aiming to get closer to
compliance with the C++0x standard as interpreted by gcc and clang
(compile with std=c++0x and -pedantic-errors). In particular, the
patch cleans up enums where the last item was succeded by a comma,
namespaces closed by a curcly brace followed by a semi-colon, and the
use of the GNU-extension typeof (replaced by templated functions). It
does not address variable-length arrays, zero-size arrays, anonymous
structs, range expressions in switch statements, and the use of long
long. The generated CPU code also has a large number of issues that
remain to be fixed, mainly related to overflows in implicit constant
conversion (due to shifts).
Making the CheckerCPU a runtime time option requires the code to be compatible
with ISAs other than ARM. This patch adds the appropriate function
stubs to allow compilation.
This patch adds a creation-time check to the CPU to ensure that the
interrupt controller is created for the cases where it is needed,
i.e. if the CPU is not being switched in later and not a checker CPU.
The patch also adds the "createInterruptController" call to a number
of the regression scripts.
This patch is adding a clearer design intent to all objects that would
not be complete without a port proxy by making the proxies members
rathen than dynamically allocated. In essence, if NULL would not be a
valid value for the proxy, then we avoid using a pointer to make this
clear.
The same approach is used for the methods using these proxies, such as
loadSections, that now use references rather than pointers to better
reflect the fact that NULL would not be an acceptable value (in fact
the code would break and that is how this patch started out).
Overall the concept of "using a reference to express unconditional
composition where a NULL pointer is never valid" could be done on a
much broader scale throughout the code base, but for now it is only
done in the locations affected by the proxies.
This patch continues the unification of how the different CPU models
create and share their instruction and data ports. Most importantly,
it forces every CPU to have an instruction and a data port, and gives
these ports explicit getters in the BaseCPU (getDataPort and
getInstPort). The patch helps in simplifying the code, make
assumptions more explicit, andfurther ease future patches related to
the CPU ports.
The biggest changes are in the in-order model (that was not modified
in the previous unification patch), which now moves the ports from the
CacheUnit to the CPU. It also distinguishes the instruction fetch and
load-store unit from the rest of the resources, and avoids the use of
indices and casting in favour of keeping track of these two units
explicitly (since they are always there anyways). The atomic, timing
and O3 model simply return references to their already existing ports.
1. Updates the Branch Predictor correctly to the state
just after a mispredicted branch, if a squash occurs.
2. If a BTB does not find an entry, the branch is predicted not taken.
The global history is modified to correctly reflect this prediction.
3. Local history is now updated at the fetch stage instead of
execute stage.
4. In the Update stage of the branch predictor the local predictors are
now correctly updated according to the state of local history during
fetch stage.
This patch also improves performance by as much as 17% on some benchmarks
This change adds a master id to each request object which can be
used identify every device in the system that is capable of issuing a request.
This is part of the way to removing the numCpus+1 stats in the cache and
replacing them with the master ids. This is one of a series of changes
that make way for the stats output to be changed to python.
Because there are no longer architecture independent but specialized functions
in arch/XXX/faults.hh, code that isn't using the faults from a particular ISA
no longer needs to be able to include them through the switching header file
arch/faults.hh. By removing that header file (arch/faults.hh), the potential
interface between ISA code and non ISA code is narrowed.
This patch adds the necessary flags to the SConstruct and SConscript
files for compiling using clang 2.9 and later (on Ubuntu et al and OSX
XCode 4.2), and also cleans up a bunch of compiler warnings found by
clang. Most of the warnings are related to hidden virtual functions,
comparisons with unsigneds >= 0, and if-statements with empty
bodies. A number of mismatches between struct and class are also
fixed. clang 2.8 is not working as it has problems with class names
that occur in multiple namespaces (e.g. Statistics in
kernel_stats.hh).
clang has a bug (http://llvm.org/bugs/show_bug.cgi?id=7247) which
causes confusion between the container std::set and the function
Packet::set, and this is currently addressed by not including the
entire namespace std, but rather selecting e.g. "using std::vector" in
the appropriate places.
This patch cleans up forward declarations and a member-function
prototype that still referred to the old FunctionalPort, VirtualPort
and TranslatingPort. There is no change in functionality.
