Re: Slow Kernel Boot

[Izik Eidus <izike-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Dave Hansen wrote:
> With kvm-44, I thought my kernel was freezing during boot if I gave it
> 1G of RAM.  But, it boots fine with 512M.
>
> So, I instrumented the kernel, and found out that it is just taking a
> long time to memset a 58MB area of memory for mem_map[].  It appears to
> be taking a mmio_exit for every access of every byte of memory.  The end
> result is a ~100kbps memset() speed.  Yes, 100 kilobytes/sec.
>
> I just tried kvm from git, and the kernel doesn't even get that far.  I
> see this in debugfs
>  
> 	insn_emulation:1393985
>
> even before I get a single kernel message.  And it keeps going up, fast.
> I can get the kernel to boot just fine if I give it less than 896MB of
> RAM.
>
> kvm-44 boots long enough for me to see a really funky e820 table:
>
> BIOS-provided physical RAM map:
>  BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
>  BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
>  BIOS-e820: 00000000000e8000 - 0000000000100000 (reserved)
>  BIOS-e820: 0000000000100000 - 00000000fffbd000 (usable)
>  BIOS-e820: 00000000fffbd000 - 00000000ffff0000 (reserved)
>
> Note that this is with '-m 1G'!!  It looks to me like one of those
> sections is basically from 0x100000 up to ~4G and *usable*.  That
> doesn't look right.
>   
yea it really dont look right, it look like it for some reason map the 
whole memory up untill the bios to the kernel as memory
it even map it on the pci hole so...
hrmmm, very weird,

what is your host info (32/64 amd/intel kernel...)? and what is the 
guest info (kernel 32/64...) ?
and what happen if you run it with -no-kvm ?
and are you using new kvm-userspace as well? or just new kvm kernel 
modules (or is is the oppiste?)


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