Hi Patrick,
I don’t dare say exactly. I suspect it is the interplay of the multi-channel
DRAM and the oddity of having one set of controllers per memory range (and the
chopped up ranges you get with >2 GB worth of memory). If you relly need this
working now then a few Python prints along with gdb is probably the best way to
go.
The more long term solution to this is probably proper support for memory
aliasing. In short we allocate a big chunk of contiguous address space on some
higher addresses for the entire DRAM (4 GB in your case), and them map part of
that (2 GB most likely) to a lower range. I’m working on a patch for this, and
it should not be too long before it is on RB.
Andreas
From: Patrick via gem5-users <[email protected]<mailto:[email protected]>>
Reply-To: Patrick <[email protected]<mailto:[email protected]>>, gem5 users
mailing list <[email protected]<mailto:[email protected]>>
Date: Monday, 8 December 2014 20:36
To: gem5 users mailing list <[email protected]<mailto:[email protected]>>
Subject: Re: [gem5-users] Why does gem5 create twice the number of memory
controllers and simulate 1GB memory more while sepecified memory size is
greater than 3GB
Andreas,
Below is the command line I am using.
./build/X86/gem5.opt --debug-flags=PatrickTLB,PatrickPageTableWalker
--debug-file=out ./configs/example/fs.py --cpu-type=timing --caches --l2cache
--mem-channels=4 -b boot
"boot" is a benchmark I added that initializes SysConfig to use 4GB of memory
(i.e. SysConfig('boot.rcS','4GB') ).
The "PatrickTLB" and "PatrickPageTableWalker" are debug flags I added, but I
assume they aren't relevant to my question here.
Any help is appreciated.
Regards,
Patrick
On Mon, Dec 8, 2014 at 11:09 AM, Andreas Hansson
<[email protected]<mailto:[email protected]>> wrote:
Patrick,
Could you elaborate on the command line you are using when experiencing this
error?
Thanks,
Andreas
From: Patrick via gem5-users <[email protected]<mailto:[email protected]>>
Reply-To: Patrick <[email protected]<mailto:[email protected]>>, gem5 users
mailing list <[email protected]<mailto:[email protected]>>
Date: Monday, 8 December 2014 17:51
To: gem5 users mailing list <[email protected]<mailto:[email protected]>>
Subject: Re: [gem5-users] Why does gem5 create twice the number of memory
controllers and simulate 1GB memory more while sepecified memory size is
greater than 3GB
Sandnon,
When I try to run with > 3GB, I get an error message saying:
"panic: Cannot test intersection of interleaved range [0x100000000 :
0x13fffffff], [14 : 13] = 1"
Were you able to get around this somehow, or did you not see this?
Any help is appreciated.
Regards,
Patrick
On Tue, Oct 14, 2014 at 8:51 PM, sandnon via gem5-users
<[email protected]<mailto:[email protected]>> wrote:
Hi all,
When I ran full system mode of gem5 with --mem-size=4GB and
--disk-image=/dist/m5/system/disks/linux-x86.img, it gave me a warn message that
> warn: Physical memory size specified is 4GB which is greater than 3GB. Twice
> the number of memory controllers would be created.
And the slave terminal said
> Memory: 4043292k/5242880k available (3742k kernel code, 150376k reserved,
> 1874k data, 232k init)
It seems gem5 simulated 5GB for me while I requested for 4GB.
I searched it and found a
[changeset](http://repo.gem5.org/gem5?cmd=changeset;node=fae4550d2103) which
said
> On the PC platform, the memory region 0xC0000000-0xFFFFFFFF is reserved for
> various devices. Hence, if the physical memory size is greater than 3GB, we
> need to split it into two parts.
I still have no idea why gem5 do that even I saw the comments aforementioned. I
know linux kernel will reserve 0xC0000000-0XFFFFFFFF virtual address for
kernel. But I'm not sure if it is related.
I conclude my questions again
- Why does gem5 create twice the number of memory controllers while physical
memory size is greater than 3GB
- Why does gem5 simulate 1GB memory more while specified memory size is
greater than 3GB
---
Sincerely,
Sandnon
_______________________________________________
gem5-users mailing list
[email protected]<mailto:[email protected]>
http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users
-- IMPORTANT NOTICE: The contents of this email and any attachments are
confidential and may also be privileged. If you are not the intended recipient,
please notify the sender immediately and do not disclose the contents to any
other person, use it for any purpose, or store or copy the information in any
medium. Thank you.
ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered
in England & Wales, Company No: 2557590
ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ,
Registered in England & Wales, Company No: 2548782
-- IMPORTANT NOTICE: The contents of this email and any attachments are
confidential and may also be privileged. If you are not the intended recipient,
please notify the sender immediately and do not disclose the contents to any
other person, use it for any purpose, or store or copy the information in any
medium. Thank you.
ARM Limited, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ, Registered
in England & Wales, Company No: 2557590
ARM Holdings plc, Registered office 110 Fulbourn Road, Cambridge CB1 9NJ,
Registered in England & Wales, Company No: 2548782_______________________________________________
gem5-users mailing list
[email protected]
http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users
