Re: [Xen-ia64-devel] PATCH: xencomm [2]

[Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>]

Hi, Aron

>However on ia64 this isn't sufficient.  We need either for the modules
>to load *earlier* (such as in the initramfs) or we need to use
>dom0_mem=1G (for example)
>
>I have some questions, though:
>
>1. On x86, all of the memory is assigned to dom0, then it balloons to
>   give memory to unpriv'd domains.  Why does ia64 give only 512M to
>   dom0 instead of doing the same as x86?
>
I don't know, but I think this is for historical reasons.
Old Xen/IA64 (about 1 year ago) used only about 2GB.
So I think dom0_mem was defined to 512MB.

I made the patch, but the patch have a problem.
I'm debug it now.

>2. Juan says that he can boot x86 xen with only 128M of memory, and
>   there's still enough physically contiguous to load blkbk and netbk
>   when xend loads.  So why does ia64 need 8x the memory to do avoid
>   fragmentation?  It seems like we must be doing something wrong for
>   memory to fragment so quickly...!
I also don't know about it.
This is strange, but insmod blkbk will fail in the following case on x86.
1. "chkconfig xend off"
2. and do many operations after boot
3. then "service xend start"
   ---> insmod blkbk fail (probably)


>On PAE the problem was "fixed" by loading blkbk/netbk in
>/etc/init.d/xend.  This moves the module load early enough in the
>system boot to fix it on that arch.
So the above solution is not good.
If we choice the early module load solution,
we should add it into rc.sysinit.

Best Regards,

Akio Takebe


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