[gem5-users] Support for multicore for X86 O3 CPU Full System with classical memory

Discussion:

Shehab Elsayed

2018-11-16 15:20:20 UTC

Hello All,

I am running into trouble running full system simulation with 2 X86 O3
cores and classical memory system where the system seems to get stuck
during script execution. I read in other (relatively) old posts that
multicore might not be supported for this configuration (X86-O3-classical
memory).

I was just wondering if this is still the case or if I should investigate
more to see if I am doing something wrong.

The same configuration works for 1 X86 O3 core as well as for multicore
AtomicSimple cores.

Thanks in advance,

Shehab

Gabe Black

2018-11-16 22:38:13 UTC

Permalink

I'm not specifically aware of a problem with O3 and multicore on x86. Can
you point out the posts you're referring to? O3 and multicore both add a
dimension of complexity, so that would be a more likely place for bugs to
crop up.

Gabe

Post by Shehab Elsayed
Hello All,
I am running into trouble running full system simulation with 2 X86 O3
cores and classical memory system where the system seems to get stuck
during script execution. I read in other (relatively) old posts that
multicore might not be supported for this configuration (X86-O3-classical
memory).
I was just wondering if this is still the case or if I should investigate
more to see if I am doing something wrong.
The same configuration works for 1 X86 O3 core as well as for multicore
AtomicSimple cores.
Thanks in advance,
Shehab
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Shehab Elsayed

2018-11-20 22:50:28 UTC

Permalink

This is the post I was referring to:
https://www.mail-archive.com/gem5-***@gem5.org/msg10498.html

The second paragraph describes the problem with more than O3 CPU, Full
System and Classical Memory system at the time of the post.

Post by Gabe Black
I'm not specifically aware of a problem with O3 and multicore on x86. Can
you point out the posts you're referring to? O3 and multicore both add a
dimension of complexity, so that would be a more likely place for bugs to
crop up.
Gabe

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Gabe Black

2018-11-21 00:03:43 UTC

Permalink

Ok, that sounds plausible. I don't know the details of what was needed
before, but basically it sounds like x86's LOCK prefix, which makes some
read/modify/write type operations which act on memory atomic, may not have
been completely supported by the caches which would enforce that behavior.
Some work has been done related to atomic memory operations since that
thread, but again I'm not sure exactly what was done or how it applies to
x86.

Perhaps some ARM folks can comment? I think they were the ones that added
the new atomic op mechanism.

Gabe

Post by Shehab Elsayed
The second paragraph describes the problem with more than O3 CPU, Full
System and Classical Memory system at the time of the post.

Post by Shehab Elsayed
Hello All,
I am running into trouble running full system simulation with 2 X86 O3
cores and classical memory system where the system seems to get stuck
during script execution. I read in other (relatively) old posts that
multicore might not be supported for this configuration (X86-O3-classical
memory).
I was just wondering if this is still the case or if I should
investigate more to see if I am doing something wrong.
The same configuration works for 1 X86 O3 core as well as for multicore
AtomicSimple cores.
Thanks in advance,
Shehab
_______________________________________________
gem5-users mailing list
http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users

_______________________________________________
gem5-users mailing list
http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users