Hey George, I had indeed looked into the options for compiling kernels for Gem5, and it > seems the latest kernel that there are gem5 patches for is 2.6.27: > > http://repo.gem5.org/linux-patches/file/0ab58d9bd9a5/stable > > I didn't try compiling a newer kernel without patches, but looking at the > changes these patches make, they they are necessary. >
That's correct. I had put together comparable patches for an x86 kernel build a couple years ago, but there were changes to Linux that made them unnecessary for x86 after ~2.6.22. My question on the previous email was if anyone knows how many CPUs the > pre-compiled 2.6.28.4 kernel at the parsec website was compiled for: > > http://www.cs.utexas.edu/~cart/parsec_m5/ > I believe I configured this kernel for up to 64 cores. We had trouble getting gem5 to work with more than that due to x86 devices (see more below), so we only configured the kernel to work with up to 64. I did try, however, to run more than 128 X86 CPUs with the latest gem5 > stable version and I got a failed assertion somewhere in the X86 device. > This probably means that X86 with more than 128 cores is not supported, > right? Is that also true for syscall emulation? > Yes, in full-system simulation, the APIC device for x86 has a hard limitation on the number of cores that it supports. I believe we'd need to add an x2APIC device and make appropriate tweaks to the interrupt controllers in order to surpass this limitation in full-system mode. As far as I'm aware, SE mode should work with more than 64 cores. Hope this helps, Joel > *From:* Joel Hestness <[email protected]> > *To:* George Michelogiannakis <[email protected]>; gem5 users > mailing list <[email protected]> > *Sent:* Friday, August 2, 2013 10:07 AM > *Subject:* Re: [gem5-users] x86 kernels > > Hi George, > I think you're looking for CONFIG_SMP and CONFIG_NR_CPUS. There are > some details here: http://cateee.net/lkddb/web-lkddb/NR_CPUS.html. > > One thing to note is that sometimes the Linux kconfigs set range > restrictions on the number of CPU cores. Sometimes these limitations are > based on hardware restrictions, such as the design of interrupt devices, > and other times they are soft limits that can be fudged for running in gem5 > (I don't recall the details off-hand, but it involves modifying a range > parameter in kconfigs - check out: > https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt). > > Hope this helps, > Joel > > > On Thu, Aug 1, 2013 at 6:51 PM, George Michelogiannakis < > [email protected]> wrote: > > Hi all, > A quick question: I looked through the pre-compiled SMP kernel's config > file on the wiki, but I couldn't find the option for the maximum number of > CPUs it supports. Do you have that available? Also, Did anyone try > compiling the latest kernel (2.6.34) with this config file? > > Thanks, > George M > > _______________________________________________ > gem5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/gem5-users > > > > > -- > Joel Hestness > PhD Student, Computer Architecture > Dept. of Computer Science, University of Wisconsin - Madison > http://pages.cs.wisc.edu/~hestness/ > > > -- Joel Hestness PhD Student, Computer Architecture Dept. of Computer Science, University of Wisconsin - Madison http://pages.cs.wisc.edu/~hestness/
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