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mem: Address mapping with fine-grained channel interleaving

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This patch adds an address mapping scheme where the channel
interleaving takes place on a cache line granularity. It is similar to
the existing RaBaChCo that interleaves on a DRAM page, but should give
higher performance when there is less locality in the address
stream.
This commit is contained in:
Andreas Hansson
2013-04-22 13:20:34 -04:00
parent e61799aa7c
commit e23e3bea8b
2 changed files with 37 additions and 18 deletions
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10
src/mem/SimpleDRAM.py
View File

@@ -44,11 +44,11 @@ from AbstractMemory import *
class MemSched(Enum): vals = ['fcfs', 'frfcfs']
# Enum for the address mapping. With Ra, Co, Ba and Ch denoting rank,
# column, bank and channel, respectively, and going from MSB to LSB,
# the two schemes available are RaBaChCo and CoRaBaCh, either
# optimising for sequential accesses hitting in the open row, or
# maximising parallelism.
class AddrMap(Enum): vals = ['RaBaChCo', 'CoRaBaCh']
# column, bank and channel, respectively, and going from MSB to LSB.
# Available are RaBaChCo and RaBaCoCh, that are suitable for an
# open-page policy, optimising for sequential accesses hitting in the
# open row. For a closed-page policy, CoRaBaCh maximises parallelism.
class AddrMap(Enum): vals = ['RaBaChCo', 'RaBaCoCh', 'CoRaBaCh']
# Enum for the page policy, either open or close.
class PageManage(Enum): vals = ['open', 'close']

45
src/mem/simple_dram.cc
View File

@@ -118,6 +118,11 @@ SimpleDRAM::init()
panic("Interleaving of %s doesn't match RaBaChCo address map\n",
name());
}
} else if (addrMapping == Enums::RaBaCoCh) {
if (bytesPerCacheLine != range.granularity()) {
panic("Interleaving of %s doesn't match RaBaCoCh address map\n",
name());
}
} else if (addrMapping == Enums::CoRaBaCh) {
if (bytesPerCacheLine != range.granularity())
panic("Interleaving of %s doesn't match CoRaBaCh address map\n",
@@ -173,11 +178,9 @@ SimpleDRAM::writeQueueFull() const
SimpleDRAM::DRAMPacket*
SimpleDRAM::decodeAddr(PacketPtr pkt)
{
// decode the address based on the address mapping scheme
//
// with Ra, Co, Ba and Ch denoting rank, column, bank and channel,
// respectively, and going from MSB to LSB, the two schemes are
// RaBaChCo and CoRaBaCh
// decode the address based on the address mapping scheme, with
// Ra, Co, Ba and Ch denoting rank, column, bank and channel,
// respectively
uint8_t rank;
uint16_t bank;
uint16_t row;
@@ -188,20 +191,36 @@ SimpleDRAM::decodeAddr(PacketPtr pkt)
addr = addr / bytesPerCacheLine;
// we have removed the lowest order address bits that denote the
// position within the cache line, proceed and select the
// appropriate bits for bank, rank and row (no column address is
// needed)
// position within the cache line
if (addrMapping == Enums::RaBaChCo) {
// the lowest order bits denote the column to ensure that
// 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
// take out the channel part of the address
addr = addr / channels;
// after the channel bits, we get the bank bits to interleave
// after the channel bits, get the bank bits to interleave
// over the banks
bank = addr % banksPerRank;
addr = addr / banksPerRank;
// after the bank, we get the rank bits which thus interleaves
// over the ranks
rank = addr % ranksPerChannel;
addr = addr / ranksPerChannel;
// lastly, get the row bits
row = addr % rowsPerBank;
addr = addr / rowsPerBank;
} else if (addrMapping == Enums::RaBaCoCh) {
// take out the channel part of the address
addr = addr / channels;
// next, the column
addr = addr / linesPerRowBuffer;
// after the column bits, we get the bank bits to interleave
// over the banks
bank = addr % banksPerRank;
addr = addr / banksPerRank;
@@ -474,7 +493,7 @@ SimpleDRAM::printParams() const
string scheduler = memSchedPolicy == Enums::fcfs ? "FCFS" : "FR-FCFS";
string address_mapping = addrMapping == Enums::RaBaChCo ? "RaBaChCo" :
"CoRaBaCh";
(addrMapping == Enums::RaBaCoCh ? "RaBaCoCh" : "CoRaBaCh");
string page_policy = pageMgmt == Enums::open ? "OPEN" : "CLOSE";
DPRINTF(DRAM,