The first two levels (L0, L1) are private to the core, the third level (L2)is
possibly shared. The protocol supports clustered designs. For example, one
can have two sets of two cores. Each core has an L0 and L1 cache. There are
two L2 controllers where each set accesses only one of the L2 controllers.
A cluster over here means a set of controllers that can be accessed only by a
certain set of cores. For example, consider a two level hierarchy. Assume
there are 4 L1 controllers (private) and 2 L2 controllers. We can have two
different hierarchies here:
a. the address space is partitioned between the two L2 controllers. Each L1
controller accesses both the L2 controllers. In this case, each L1 controller
is a cluster initself.
b. both the L2 controllers can cache any address. An L1 controller has access
to only one of the L2 controllers. In this case, each L2 controller
along with the L1 controllers that access it, form a cluster.
This patch allows for each controller to have a cluster ID, which is 0 by
default. By setting the cluster ID properly, one can instantiate hierarchies
with clusters. Note that the coherence protocol might have to be changed as
well.
This patch fixes couple of bugs in the L2 controller of the mesi cmp
directory protocol.
1. The state MT_I was transitioning to NP on receiving a clean writeback
from the L1 controller. This patch makes it inform the directory controller
about the writeback.
2. The L2 controller was sending the dirty bit to the L1 controller and the
L2 controller used writeback from the L1 controller to update the dirty bit
unconditionally. Now, the L1 controller always assumes that the incoming
data is clean. The L2 controller updates the dirty bit only when the L1
controller writes to the block.
3. Certain unused functions and events are being removed.
This patch replaces max_in_port_rank with the number of inports. The use of
max_in_port_rank was causing spurious re-builds and incorrect initialization
of variables in ruby related regression tests. This was due to the variable
value being used across threads while compiling when it was not meant to be.
Since the number of inports is state machine specific value, this problem
should get solved.
The directory controller should not have the sharer field since there is
only one level 2 cache. Anyway the field was not in use. The owner field
was being used to track the l2 cache version (in case of distributed l2) that
has the cache block under consideration. The information is not required
since the version of the level 2 cache can be obtained from a subset of the
address bits.
This patch fixes a number of stats accounting issues in the DRAM
controller. Most importantly, it separates the system interface and
DRAM interface so that it is clearer what the actual DRAM bandwidth
(and consequently utilisation) is.
This patch unifies the request selection across read and write queues
for FR-FCFS scheduling policy. It also fixes the request selection
code to prioritize the row hits present in the request queues over the
selection based on earliest bank availability.
This patch adds a basic adaptive version of the open-page policy that
guides the decision to keep open or close by looking at the contents
of the controller queues. If no row hits are found, and bank conflicts
are present, then the row is closed by means of an auto
precharge. This is a well-known technique that should improve
performance in most use-cases.
This patch removes the untimed while loop in the write scheduling
mechanism and now schedule commands taking into account the minimum
timing constraint. It also introduces an optimization to track write
queue size and switch from writes to reads if the number of write
requests fall below write low threshold.
This patch adds the tRRD parameter to the DRAM controller. With the
recent addition of the actAllowedAt member for each bank, this
addition is trivial.
This patch changes the tXAW constraint so that it is enforced per rank
rather than globally for all ranks in the channel. It also avoids
using the bank freeAt to enforce the activation limit, as doing so
also precludes performing any column or row command to the
DRAM. Instead the patch introduces a new variable actAllowedAt for the
banks and use this to track when a potential activation can occur.
This patch fixes the controller when a write threshold of 100% is
used. Earlier for 100% write threshold no data is written to memory
as writes never get triggered since this corner case is not
considered.
This patch changes the FCFS bit of FR-FCFS such that requests that
target the earliest available bank are picked first (as suggested in
the original work on FR-FCFS by Rixner et al). To accommodate this we
add functionality to identify a bank through a one-dimensional
identifier (bank id). The member names of the DRAMPacket are also
update to match the style guide.
This patch changes the time the controller is woken up to take the
next scheduling decisions. tRAS is now handled in estimateLatency and
doDRAMAccess and we do not need to worry about it at scheduling
time. The earliest we need to wake up is to do a pre-charge, row
access and column access before the bus becomes free for use.
This patch adds an explicit tRAS parameter to the DRAM controller
model. Previously tRAS was, rather conservatively, assumed to be tRCD
+ tCL + tRP. The default values for tRAS are chosen to match the
previous behaviour and will be updated later.
This patch adds missing initializations of the SenderMachine field of
out_msg's when thery are created in the L2 cache controller of the
MOESI_CMP_directory coherence protocol. When an out_msg is created and this
field is left uninitialized, it is set to the default value MachineType_NUM.
This causes a panic in the MachineType_to_string function when gem5 is
executed with the Ruby debug flag on and it tries to print the message.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
This patch fixes a problem where in Garnet, the enqueue time in the
VCallocator and the SWallocator which is of type Cycles was being stored
inside a variable with int type.
This lead to a known problem restoring checkpoints with garnet & the fixed
pipeline enabled. That value was really big and didn't fit in the variable
overflowing it, therefore some conditions on the VC allocation stage & the
SW allocation stage were not met and the packets didn't advance through the
network, leading to a deadlock panic right after the checkpoint was restored.
Committed by: Nilay Vaish <nilay@cs.wisc.edu>
The CoherentBus eventually got virtual methods for its interface. The
"virtuality" of the CoherentBus, however, comes already from the virtual
interface of the bus' ports. There is no need to add another layer of virtual
functions, here.
Get rid of non-deterministic "stats" in ruby.stats output
such as time & date of run, elapsed & CPU time used,
and memory usage. These values cause spurious
miscomparisons when looking at output diffs (though
they don't affect regressions, since the regressions
pass/fail status currently ignores ruby.stats entirely).
Most of this information is already captured in other
places (time & date in stdout, elapsed time & mem usage
in stats.txt), where the regression script is smart
enough to filter it out. It seems easier to get rid of
the redundant output rather than teaching the
regression tester to ignore the same information in
two different places.
ASI_BITS in the Request object were originally used to store a memory
request's ASI on SPARC. This is not the case any more since other ISAs
use the ASI bits to store architecture-dependent information. This
changeset renames the ASI_BITS to ARCH_BITS which better describes
their use. Additionally, the getAsi() accessor is renamed to
getArchFlags().
Using address bit 63 to identify generic IPRs caused problems on
SPARC, where IPRs are heavily used. This changeset redefines how
generic IPRs are identified. Instead of using bit 63, we now use a
separate flag (GENERIC_IPR) a memory request.
This patch ensures that a dequeue event is not scheduled if the memory
controller is waiting for a retry already. Without this check it is
possible for the controller to attempt sending something whilst
already having one packet that is in retry, thus causing the bus to
have an assertion failure.
The Topology source sets up input and output buffers for each of the external
nodes of a topology by indexing on Ruby's generated controller unique IDs.
These unique IDs are found by adding the MachineType_base_number to the version
number of each controller (see any generated *_Controller.cc - init() calls
getToNetQueue and getFromNetQueue using m_version + base). However, the
Topology object used the cntrl_id - which is required to be unique across all
controllers - to index the controllers list as they are being connected to
their input and output buffers. If the cntrl_ids did not match the Ruby unique
ID, the throttles end up connected to incorrectly indexed nodes in the network,
resulting in packets traversing incorrect network paths. This patch fixes the
Topology indexing scheme by using the Ruby unique ID to match that of the
SimpleNetwork buffer vectors.
The previous changeset (9863:9483739f83ee) used STL vector containers to
dynamically allocate stats in the Ruby SimpleNetwork, Switch and Throttle. For
gcc versions before at least 4.6.3, this causes the standard vector allocator
to call Stats copy constructors (a no-no, since stats should be allocated in
the body of each SimObject instance). Since the size of these stats arrays is
known at compile time (NOTE: after code generation), this patch changes their
allocation to be static rather than using an STL vector.
This patch makes it possible to once again build gem5 without any
ISA. The main purpose is to enable work around the interconnect and
memory system without having to build any CPU models or device models.
The regress script is updated to include the NULL ISA target. Currently
no regressions make use of it, but all the testers could (and perhaps
should) transition to it.
--HG--
rename : build_opts/NOISA => build_opts/NULL
rename : src/arch/noisa/SConsopts => src/arch/null/SConsopts
rename : src/arch/noisa/cpu_dummy.hh => src/arch/null/cpu_dummy.hh
rename : src/cpu/intr_control.cc => src/cpu/intr_control_noisa.cc
This patch updates the stats to reflect the: 1) addition of the
internal queue in SimpleMemory, 2) moving of the memory class outside
FSConfig, 3) fixing up of the 2D vector printing format, 4) specifying
burst size and interface width for the DRAM instead of relying on
cache-line size, 5) performing merging in the DRAM controller write
buffer, and 6) fixing how idle cycles are counted in the atomic and
timing CPU models.
The main reason for bundling them up is to minimise the changeset
size.
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.
