This patch enables modeling a complete Hybrid Memory Cube (HMC) device. It
highly reuses the existing components in gem5's general memory system with some
small modifications. This changeset requires additional patches to model a
complete HMC device.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
Transaction Level Modeling (TLM2.0) is widely used in industry for creating
virtual platforms (IEEE 1666 SystemC). This patch contains a standard compliant
implementation of an external gem5 port, that enables the usage of gem5 as a
TLM initiator component in SystemC based virtual platforms. Both TLM coding
paradigms loosely timed (b_transport) and aproximately timed (nb_transport) are
supported.
Compared to the original patch a TLM memory manager was added. Furthermore, the
transaction object was removed and for each TLM payload a PacketPointer that
points to the original gem5 packet is added as an TLM extension. For event
handling single events are now created.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This patch adds an example configuration in ext/sst/tests/ that allows
an SST/gem5 instance to simulate a 4-core AArch64 system with SST's
memHierarchy components providing all the caches and memories.
This patch uses the recently added XOR hashing capabilities for the
DRAM channel interleaving. This avoids channel biasing due to strided
access patterns.
This patch changes the DRAM channel interleaving default behaviour to
be more representative. The default address mapping (RoRaBaCoCh) moves
the channel bits towards the least significant bits, and uses 128 byte
as the default channel interleaving granularity.
These defaults can be overridden if desired, but should serve as a
sensible starting point for most use-cases.
This patch gives the user direct influence over the number of DRAM
ranks to make it easier to tune the memory density without affecting
the bandwidth (previously the only means of scaling the device count
was through the number of channels).
The patch also adds some basic sanity checks to ensure that the number
of ranks is a power of two (since we rely on bit slices in the address
decoding).
This patch is the final in the series. The whole series and this patch in
particular were written with the aim of interfacing ruby's directory controller
with the memory controller in the classic memory system. This is being done
since ruby's memory controller has not being kept up to date with the changes
going on in DRAMs. Classic's memory controller is more up to date and
supports multiple different types of DRAM. This also brings classic and
ruby ever more close. The patch also changes ruby's memory controller to
expose the same interface.
This patch moves code for instantiating a single memory controller from
the function config_mem() to a separate function. This is being done
so that memory controllers can be instantiated without assuming that
they will be attached to the system in a particular fashion.
This patch renames the not-so-simple SimpleDRAM to a more suitable
DRAMCtrl. The name change is intended to ensure that we do not send
the wrong message (although the "simple" in SimpleDRAM was originally
intended as in cleverly simple, or elegant).
As the DRAM controller modelling work is being presented at ISPASS'14
our hope is that a broader audience will use the model in the future.
--HG--
rename : src/mem/SimpleDRAM.py => src/mem/DRAMCtrl.py
rename : src/mem/simple_dram.cc => src/mem/dram_ctrl.cc
rename : src/mem/simple_dram.hh => src/mem/dram_ctrl.hh
This patch adds the row bits to the name of the address mapping
schemes to make it more clear that all the current schemes places the
row bits as the most significant bits.
This patch adds DRAMSim2 as a memory controller by wrapping the
external library and creating a sublass of AbstractMemory that bridges
between the semantics of gem5 and the DRAMSim2 interface.
The DRAMSim2 wrapper extracts the clock period from the config
file. There is no way of extracting this information from DRAMSim2
itself, so we simply read the same config file and get it from there.
To properly model the response queue, the wrapper keeps track of how
many transactions are in the actual controller, and how many are
stacking up waiting to be sent back as responses (in the wrapper). The
latter requires us to move away from the queued port and manage the
packets ourselves. This is due to DRAMSim2 not having any flow control
on the response path.
DRAMSim2 assumes that the transactions it is given are matching the
burst size of the choosen memory. The wrapper checks to ensure the
cache line size of the system matches the burst size of DRAMSim2 as
there are currently no provisions to split the system requests. In
theory we could allow a cache line size smaller than the burst size,
but that would lead to inefficient use of the DRAM, so for not we
fatal also in this case.
This patch adds support for specifying multi-channel memory
configurations on the command line, e.g. 'se/fs.py
--mem-type=ddr3_1600_x64 --mem-channels=4'. To enable this, it
enhances the functionality of MemConfig and moves the existing
makeMultiChannel class method from SimpleDRAM to the support scripts.
The se/fs.py example scripts are updated to make use of the new
feature.
This patch changes the class names of the variuos DRAM configurations
to better reflect what memory they are based on. The speed and
interface width is now part of the name, and also the alias that is
used to select them on the command line.
Some minor changes are done to the actual parameters, to better
reflect the named configurations. As a result of these changes the
regressions change slightly and the stats will be bumped in a separate
patch.
This patch adds a typical (leaning towards fast) LPDDR3 configuration
based on publically available data. As expected, it looks very similar
to the LPDDR2-S4 configuration, only with a slightly lower burst time.
This patch enables selection of the memory controller class through a
mem-type command-line option. Behind the scenes, this option is
treated much like the cpu-type, and a similar framework is used to
resolve the valid options, and translate the short-hand description to
a valid class.
The regression scripts are updated with a hardcoded memory class for
the moment. The best solution going forward is probably to get the
memory out of the makeSystem functions, but Ruby complicates things as
it does not connect the memory controller to the membus.
--HG--
rename : configs/common/CpuConfig.py => configs/common/MemConfig.py
