Hi Prathap,
It would very well be a bug. We have got a small fix for the FRFCFS about to go
out (but it should not affect your scenario assuming It is a single rank):
diff --git a/src/mem/dram_ctrl.cc b/src/mem/dram_ctrl.cc
--- a/src/mem/dram_ctrl.cc
+++ b/src/mem/dram_ctrl.cc
@@ -1483,8 +1489,8 @@
// 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;
}
Could you give that a spin?
Thanks,
Andreas
From: Prathap Kolakkampadath via gem5-users
<gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Reply-To: Prathap Kolakkampadath
<kvprat...@gmail.com<mailto:kvprat...@gmail.com>>, gem5 users mailing list
<gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Date: Friday, 14 November 2014 00:11
To: gem5 users mailing list <gem5-users@gem5.org<mailto:gem5-users@gem5.org>>
Subject: [gem5-users] DRAMCTRL:Seeing an unusual behaviuor with FR-FCFS
scheduler
Hi Users,
For the following scenario:
Read0 Read1 Read2 Read3 Read4 Read5 Read6 Read7 Read8 Read9 Read10 Read11
There are 12 reads in the read queue numbered in the order of arrival.
Read 0 to Read3 access same row of Bank1, Read4 access Bank0, Read5 to Read8
access same row of Bank2 and Read9 to Read11 access same row of Bank3.
According to FR-FCFS scheduler, even there is only a single request Read4 to
Bank0, it should be scheduled after the Read0 to Read3 are scheduled. Because
within the window of Read0-Read3, the Read4 would have done with precharge and
activate and ready to schedule. Though Read5 and Read9 are also ready, Read4
needs to be scheduled as the next row hit, according to FCFS.
However i see a different behaviour where Read4 is scheduled only after all
other row hits to Bank2 and Bank3 is scheduled. Also i noticed from the debug
prints that Read4 is not becoming a row_hit.
Are we missing to mark the read as row hit after precharge and activate. I am
trying to figure this out. Is my understanding correct?
Thanks,
Prathap
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