Re: Slow Kernel Boot

[Dave Hansen <haveblue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

On Tue, 2008-01-08 at 00:16 +0200, Izik Eidus wrote:
> 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...)?

64-bit intel host, kernel 2.6.24-rc5

Running kvm's current git userspace with modules from the same version.

> and what is the 
> guest info (kernel 32/64...) ?

32-bit 2.6.23-rc6-mm1

> and what happen if you run it with -no-kvm ?

Both current -git and kvm-44 seem to lock up at early kernel boot before
even early printk is available.  But, GRUB comes up in both cases. 

-no-kvm doesn't seem to change things at all.

-- Dave


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