changeset 471d390943f0 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=471d390943f0
description:
mem: Fix a bug in the DRAM controller arbitration
Fix a minor issue that affects multi-rank systems.
diffstat:
src/mem/dram_ctrl.cc | 12 +++++++++---
1 files changed, 9 insertions(+), 3 deletions(-)
diffs (29 lines):
diff -r 6d4da9dc90a1 -r 471d390943f0 src/mem/dram_ctrl.cc
--- a/src/mem/dram_ctrl.cc Tue Dec 23 09:31:18 2014 -0500
+++ b/src/mem/dram_ctrl.cc Tue Dec 23 09:31:18 2014 -0500
@@ -1477,7 +1477,13 @@
// Offset by tRCD to correlate with ACT timing variables
Tick min_cmd_at = busBusyUntil - tCL - tRCD;
- // Prioritize same rank accesses that can issue B2B
+ // if we have multiple ranks and all
+ // waiting packets are accessing a rank which was previously active
+ // then bank_mask_same_rank will be set to a value while bank_mask will
+ // remain 0. In this case, the function should return the value of
+ // bank_mask_same_rank.
+ // else if waiting packets access a rank which was previously active and
+ // other ranks, prioritize same rank accesses that can issue B2B
// Only optimize for same ranks when the command type
// does not change; do not want to unnecessarily incur tWTR
//
@@ -1485,8 +1491,8 @@
// 1) Commands that access the same rank as previous burst
// and can prep the bank seamlessly.
// 2) Commands (any rank) with earliest bank prep
- if (!switched_cmd_type && same_rank_match &&
- min_act_at_same_rank <= min_cmd_at) {
+ if ((bank_mask == 0) || (!switched_cmd_type && same_rank_match &&
+ min_act_at_same_rank <= min_cmd_at)) {
bank_mask = bank_mask_same_rank;
}
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