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authorAndreas Hansson <andreas.hansson@arm.com>2015-02-03 14:25:52 -0500
committerAndreas Hansson <andreas.hansson@arm.com>2015-02-03 14:25:52 -0500
commit5ea60a95b3d87fac6723678e07822aed512f966e (patch)
treea104cbcc0e4f15deb4ad87f6642a16ca1145ab0e
parent9aad5b45690adae9f1208b6d3cc8dfc670d54543 (diff)
downloadgem5-5ea60a95b3d87fac6723678e07822aed512f966e.tar.xz
config: Adjust DRAM channel interleaving defaults
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.
-rw-r--r--configs/common/MemConfig.py18
-rw-r--r--src/mem/DRAMCtrl.py2
2 files changed, 12 insertions, 8 deletions
diff --git a/configs/common/MemConfig.py b/configs/common/MemConfig.py
index 4692c2d0e..3d1ae4e64 100644
--- a/configs/common/MemConfig.py
+++ b/configs/common/MemConfig.py
@@ -127,7 +127,7 @@ for alias, target in _mem_aliases_all:
# Normal alias
_mem_aliases[alias] = target
-def create_mem_ctrl(cls, r, i, nbr_mem_ctrls, intlv_bits, cache_line_size):
+def create_mem_ctrl(cls, r, i, nbr_mem_ctrls, intlv_bits, intlv_size):
"""
Helper function for creating a single memoy controller from the given
options. This function is invoked multiple times in config_mem function
@@ -135,9 +135,7 @@ def create_mem_ctrl(cls, r, i, nbr_mem_ctrls, intlv_bits, cache_line_size):
"""
import math
- # The default behaviour is to interleave on cache line granularity
- cache_line_bit = int(math.log(cache_line_size, 2)) - 1
- intlv_low_bit = cache_line_bit
+ intlv_low_bit = int(math.log(intlv_size, 2))
# Create an instance so we can figure out the address
# mapping and row-buffer size
@@ -160,13 +158,13 @@ def create_mem_ctrl(cls, r, i, nbr_mem_ctrls, intlv_bits, cache_line_size):
rowbuffer_size = ctrl.device_rowbuffer_size.value * \
ctrl.devices_per_rank.value
- intlv_low_bit = int(math.log(rowbuffer_size, 2)) - 1
+ intlv_low_bit = int(math.log(rowbuffer_size, 2))
# We got all we need to configure the appropriate address
# range
ctrl.range = m5.objects.AddrRange(r.start, size = r.size(),
intlvHighBit = \
- intlv_low_bit + intlv_bits,
+ intlv_low_bit + intlv_bits - 1,
intlvBits = intlv_bits,
intlvMatch = i)
return ctrl
@@ -192,13 +190,19 @@ def config_mem(options, system):
cls = get(options.mem_type)
mem_ctrls = []
+ # The default behaviour is to interleave memory channels on 128
+ # byte granularity, or cache line granularity if larger than 128
+ # byte. This value is based on the locality seen across a large
+ # range of workloads.
+ intlv_size = max(128, system.cache_line_size.value)
+
# For every range (most systems will only have one), create an
# array of controllers and set their parameters to match their
# address mapping in the case of a DRAM
for r in system.mem_ranges:
for i in xrange(nbr_mem_ctrls):
mem_ctrl = create_mem_ctrl(cls, r, i, nbr_mem_ctrls, intlv_bits,
- system.cache_line_size.value)
+ intlv_size)
# Set the number of ranks based on the command-line
# options if it was explicitly set
if issubclass(cls, m5.objects.DRAMCtrl) and \
diff --git a/src/mem/DRAMCtrl.py b/src/mem/DRAMCtrl.py
index 4c500960a..60b3b251e 100644
--- a/src/mem/DRAMCtrl.py
+++ b/src/mem/DRAMCtrl.py
@@ -92,7 +92,7 @@ class DRAMCtrl(AbstractMemory):
# scheduler, address map and page policy
mem_sched_policy = Param.MemSched('frfcfs', "Memory scheduling policy")
- addr_mapping = Param.AddrMap('RoRaBaChCo', "Address mapping policy")
+ addr_mapping = Param.AddrMap('RoRaBaCoCh', "Address mapping policy")
page_policy = Param.PageManage('open_adaptive', "Page management policy")
# enforce a limit on the number of accesses per row