This patch changes MessageBuffer and TimerTable, two structures used for
buffering messages by components in ruby. These structures would no longer
maintain pointers to clock objects. Functions in these structures have been
changed to take as input current time in Tick. Similarly, these structures
will not operate on Cycle valued latencies for different operations. The
corresponding functions would need to be provided with these latencies by
components invoking the relevant functions. These latencies should also be
in Ticks.
I felt the need for these changes while trying to speed up ruby. The ultimate
aim is to eliminate Consumer class and replace it with an EventManager object in
the MessageBuffer and TimerTable classes. This object would be used for
scheduling events. The event itself would contain information on the object and
function to be invoked.
In hindsight, it seems I should have done this while I was moving away from use
of a single global clock in the memory system. That change led to introduction
of clock objects that replaced the global clock object. It never crossed my
mind that having clock object pointers is not a good design. And now I really
don't like the fact that we have separate consumer, receiver and sender
pointers in message buffers.
The eventual aim of this change is to pass RubySystem pointers through to
objects generated from the SLICC protocol code.
Because some of these objects need to dereference their RubySystem pointers,
they need access to the System.hh header file.
In src/mem/ruby/SConscript, the MakeInclude function creates single-line header
files in the build directory that do nothing except include the corresponding
header file from the source tree.
However, SLICC also generates a list of header files from its symbol table, and
writes it to mem/protocol/Types.hh in the build directory. This code assumes
that the header file name is the same as the class name.
The end result of this is the many of the generated slicc files try to include
RubySystem.hh, when the file they really need is System.hh. The path of least
resistence is just to rename System.hh to RubySystem.hh.
--HG--
rename : src/mem/ruby/system/System.cc => src/mem/ruby/system/RubySystem.cc
rename : src/mem/ruby/system/System.hh => src/mem/ruby/system/RubySystem.hh
Refactored the code in operateVnet(), moved partly to a new function
operateMessageBuffer(). This is required since a later patch moves to having a
wakeup event per MessageBuffer instead of one event for the entire Switch.
There are two reasons for doing so:
a. provide a source of clock to PerfectSwitch. A follow on patch removes sender
and receiver pointers from MessageBuffer means that the object owning the
buffer should have some way of providing timing info.
b. schedule events. A follow on patch removes the consumer class. So the
PerfectSwitch needs some EventManager object to schedule events on its own.
Currently the sequencer calls the function setMRU that updates the replacement
policy structures with the first level caches. While functionally this is
correct, the problem is that this requires calling findTagInSet() which is an
expensive function. This patch removes the calls to setMRU from the sequencer.
All controllers should now update the replacement policy on their own.
The set and the way index for a given cache entry can be found within the
AbstractCacheEntry structure. Use these indicies to update the replacement
policy structures.
The current Set data structure is slow and therefore is being reimplemented
using std::bitset. A maximum limit of 64 is being set on the number of
controllers of each type. This means that for simulating a system with more
controllers of a given type, one would need to change the value of the variable
NUMBER_BITS_PER_SET
We no longer use the C library based random number generator: random().
Instead we use the C++ library provided rng. So setting the random seed for
the RubySystem class has no effect. Hence the variable and the corresponding
option are being dropped.
This member indicates whether or not a particular virtual network is in use.
Instead of having a default big value for the number of virtual networks and
then checking whether a virtual network is in use, the next patch removes the
default value and the protocol configuration file would now specify the
number of virtual networks it requires.
Additionally, the patch also refactors some of the code used for computing the
virtual channel next in the round robin order.
The new serialization code (kudos to Tim Jones) moves all of the state
mangling in RubySystem to memWriteback. This makes it possible to use
the new const serialization interface.
This changeset moves the cache recorder cleanup from the checkpoint()
method to drainResume() to make checkpointing truly constant and
updates the checkpointing code to use the new interface.
The sequencer takes care of llsc accesses by calling upon functions
from the CacheMemory. This is unnecessary once the required CacheEntry object
is available. Thus some of the calls to findTagInSet() are avoided.
This patch serves to avoid name clashes with the classic cache. For
some reason having two 'SimObject' files with the same name creates
problems.
--HG--
rename : src/mem/ruby/structures/Cache.py => src/mem/ruby/structures/RubyCache.py
We no longer use the C library based random number generator: random().
Instead we use the C++ library provided rng. So setting the random seed for
the RubySystem class has no effect. Hence the variable and the corresponding
option are being dropped.
Currently the sequencer calls the function setMRU that updates the replacement
policy structures with the first level caches. While functionally this is
correct, the problem is that this requires calling findTagInSet() which is an
expensive function. This patch removes the calls to setMRU from the sequencer.
All controllers should now update the replacement policy on their own.
The set and the way index for a given cache entry can be found within the
AbstractCacheEntry structure. Use these indicies to update the replacement
policy structures.
Before this patch, while one could declare / define a function with default
argument values, but the actual function call would require one to specify
all the arguments. This patch changes the check for function arguments.
Now a function call needs to specify arguments that are at least as much as
those with default values and at most the total number of arguments taken
as input by the function.
The sequencer takes care of llsc accesses by calling upon functions
from the CacheMemory. This is unnecessary once the required CacheEntry object
is available. Thus some of the calls to findTagInSet() are avoided.
This patch eliminates the type Address defined by the ruby memory system.
This memory system would now use the type Addr that is in use by the
rest of the system.
Expose MessageBuffers from SLICC controllers as SimObjects that can be
manipulated in Python. This patch has numerous benefits:
1) First and foremost, it exposes MessageBuffers as SimObjects that can be
manipulated in Python code. This allows parameters to be set and checked in
Python code to avoid obfuscating parameters within protocol files. Further, now
as SimObjects, MessageBuffer parameters are printed to config output files as a
way to track parameters across simulations (e.g. buffer sizes)
2) Cleans up special-case code for responseFromMemory buffers, and aligns their
instantiation and use with mandatoryQueue buffers. These two special buffers
are the only MessageBuffers that are exposed to components outside of SLICC
controllers, and they're both slave ends of these buffers. They should be
exposed outside of SLICC in the same way, and this patch does it.
3) Distinguishes buffer-specific parameters from buffer-to-network parameters.
Specifically, buffer size, randomization, ordering, recycle latency, and ports
are all specific to a MessageBuffer, while the virtual network ID and type are
intrinsics of how the buffer is connected to network ports. The former are
specified in the Python object, while the latter are specified in the
controller *.sm files. Unlike buffer-specific parameters, which may need to
change depending on the simulated system structure, buffer-to-network
parameters can be specified statically for most or all different simulated
systems.
CacheMemory and DirectoryMemory lookup functions return pointers to entries
stored in the memory. Bring PerfectCacheMemory in line with this convention,
and clean up SLICC code generation that was in place solely to handle
references like that which was returned by PerfectCacheMemory::lookup.
The RubyCache (CacheMemory) latency parameter is only used for top-level caches
instantiated for Ruby coherence protocols. However, the top-level cache hit
latency is assessed by the Sequencer as accesses flow through to the cache
hierarchy. Further, protocol state machines should be enforcing these cache hit
latencies, but RubyCaches do not expose their latency to any existng state
machines through the SLICC/C++ interface. Thus, the RubyCache latency parameter
is superfluous for all caches. This is confusing for users.
As a step toward pushing L0/L1 cache hit latency into the top-level cache
controllers, move their latencies out of the RubyCache declarations and over to
their Sequencers. Eventually, these Sequencer parameters should be exposed as
parameters to the top-level cache controllers, which should assess the latency.
NOTE: Assessing these latencies in the cache controllers will require modifying
each to eliminate instantaneous Ruby hit callbacks in transitions that finish
accesses, which is likely a large undertaking.
There are 2 problems with the existing checkpoint and restore code in ruby.
The first is that when the event queue is altered by ruby during serialization,
some events that are currently scheduled cannot be found (e.g. the event to
stop simulation that always lives on the queue), causing a panic.
The second is that ruby is sometimes serialized after the memory system,
meaning that the dirty data in its cache is flushed back to memory too late
and so isn't included in the checkpoint.
These are fixed by implementing memory writeback in ruby, using the same
technique of hijacking the event queue, but first descheduling all events that
are currently on it. They are saved, along with their scheduled time, so that
the event queue can be faithfully reconstructed after writeback has finished.
Events with the AutoDelete flag set will delete themselves when they
are descheduled, causing an error when attempting to schedule them again.
This is fixed by simply not recording them when taking them off the queue.
Writeback is still implemented using flushing, so the cache recorder object,
that is created to generate the trace and manage flushing, is kept
around and used during serialization to write the trace to disk.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This patch changes the router pipeline stages from 4 to 2. The
canonical 4-stage router is conservative while a lower-latency router
with look ahead routing and speculative allocation is well acknowledged.
Sets m_stage.second to the second parameter of the function.
Then, for every place where advance_stage is called, adds
a cycle to the argument being passed.
This patch adds support that allows the replacement policy to identify each
cache block's access permission. This information can be useful when making
replacement decisions.
