changeset b1e1409922ad in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=b1e1409922ad
description:
mem: Add support for multi-channel DRAM configurations
This patch adds support for multi-channel instances of the DRAM
controller model by stripping away the channel bits in the address
decoding. The patch relies on the availiability of address
interleaving and, at this time, it is up to the user to configure the
interleaving appropriately. At the moment it is assumed that the
channel interleaving bits are immediately following the column bits
(smallest sensible interleaving). Convenience methods for building
multi-channel configurations will be added later.
diffstat:
src/mem/SimpleDRAM.py | 4 ++++
src/mem/simple_dram.cc | 29 ++++++++++++++++++++++++++++-
src/mem/simple_dram.hh | 1 +
3 files changed, 33 insertions(+), 1 deletions(-)
diffs (85 lines):
diff -r c2f393be5f14 -r b1e1409922ad src/mem/SimpleDRAM.py
--- a/src/mem/SimpleDRAM.py Fri Mar 01 13:20:21 2013 -0500
+++ b/src/mem/SimpleDRAM.py Fri Mar 01 13:20:22 2013 -0500
@@ -80,6 +80,10 @@
lines_per_rowbuffer = Param.Unsigned("Row buffer size in cache lines")
ranks_per_channel = Param.Unsigned("Number of ranks per channel")
banks_per_rank = Param.Unsigned("Number of banks per rank")
+ # only used for the address mapping as the controller by
+ # construction is a single channel and multiple controllers have
+ # to be instantiated for a multi-channel configuration
+ channels = Param.Unsigned(1, "Number of channels")
# timing behaviour and constraints - all in nanoseconds
diff -r c2f393be5f14 -r b1e1409922ad src/mem/simple_dram.cc
--- a/src/mem/simple_dram.cc Fri Mar 01 13:20:21 2013 -0500
+++ b/src/mem/simple_dram.cc Fri Mar 01 13:20:22 2013 -0500
@@ -57,7 +57,7 @@
bytesPerCacheLine(0),
linesPerRowBuffer(p->lines_per_rowbuffer),
ranksPerChannel(p->ranks_per_channel),
- banksPerRank(p->banks_per_rank), rowsPerBank(0),
+ banksPerRank(p->banks_per_rank), channels(p->channels), rowsPerBank(0),
readBufferSize(p->read_buffer_size),
writeBufferSize(p->write_buffer_size),
writeThresholdPerc(p->write_thresh_perc),
@@ -115,6 +115,23 @@
rowsPerBank = capacity / (bytesPerCacheLine * linesPerRowBuffer *
banksPerRank * ranksPerChannel);
+ if (range.interleaved()) {
+ if (channels != range.stripes())
+ panic("%s has %d interleaved address stripes but %d channel(s)\n",
+ name(), range.stripes(), channels);
+
+ if (addrMapping == Enums::openmap) {
+ if (bytesPerCacheLine * linesPerRowBuffer !=
+ range.granularity()) {
+ panic("Interleaving of %s doesn't match open address map\n",
+ name());
+ }
+ } else if (addrMapping == Enums::closemap) {
+ if (bytesPerCacheLine != range.granularity())
+ panic("Interleaving of %s doesn't match closed address map\n",
+ name());
+ }
+ }
}
void
@@ -190,6 +207,11 @@
// sequential cache lines occupy the same row
addr = addr / linesPerRowBuffer;
+ // take out the channel part of the address, note that this has
+ // to match with how accesses are interleaved between the
+ // controllers in the address mapping
+ addr = addr / channels;
+
// after the column bits, we get the bank bits to interleave
// over the banks
bank = addr % banksPerRank;
@@ -207,6 +229,11 @@
// optimise for closed page mode and utilise maximum
// parallelism of the DRAM (at the cost of power)
+ // take out the channel part of the address, not that this has
+ // to match with how accesses are interleaved between the
+ // controllers in the address mapping
+ addr = addr / channels;
+
// start with the bank bits, as this provides the maximum
// opportunity for parallelism between requests
bank = addr % banksPerRank;
diff -r c2f393be5f14 -r b1e1409922ad src/mem/simple_dram.hh
--- a/src/mem/simple_dram.hh Fri Mar 01 13:20:21 2013 -0500
+++ b/src/mem/simple_dram.hh Fri Mar 01 13:20:22 2013 -0500
@@ -378,6 +378,7 @@
const uint32_t linesPerRowBuffer;
const uint32_t ranksPerChannel;
const uint32_t banksPerRank;
+ const uint32_t channels;
uint32_t rowsPerBank;
const uint32_t readBufferSize;
const uint32_t writeBufferSize;
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