[uml-devel] many cow files with ubd_kern.c

[uml-devel] many cow files with ubd_kern.c

[James McMechan]

Once again I have been tweaking ubd_kern to support lots of disks since I 
need it for recovery
but I hit (even on a plain 2.6.15-bs1 kernel)
allocation failed: out of vmalloc space - use "vmalloc=<size>" to increse 
size
Failed to vmalloc COW bitmap
ubd0: Can't open "COW0": errno -12

but I already had vmalloc=128M (which should be the default) and 
vmalloc=256M and mem=384M on the command line.
I can't seem to locate where the equivlaent of arch/i386/kernel/setup.c has 
the vmalloc= option on arch/um though
has anyone hit something like this before each of the bitmaps should only 
take about 60M of memory and at this point I have only tried to allocate 1 
for a single 250G ubd device

This will present a larger problem when I get everything working and try to 
allocate all 10 drives worth of bitmap ~600M
I suppose I may have to go back to the paged bitmap logic but it is still a 
mess...
The multiple major numbers and C:H:S from mconsole do seem to work correctly 
though




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Re: [uml-devel] many cow files with ubd_kern.c

[Jeff Dike]

On Sat, Jan 28, 2006 at 11:11:31PM +0000, James McMechan wrote:
> allocation failed: out of vmalloc space - use "vmalloc=<size>" to increse 
> size
> Failed to vmalloc COW bitmap
> ubd0: Can't open "COW0": errno -12

I have a report (which I haven't looked into yet) of the ubd driver
double-vmallocing the bitmap.  This is the call trace of the vmallocs
as reported on IRC:

ubd_add
 enter
Attempting to vmalloc COW bitmap \"cow0\" at
 25600
cow.bitmap = 0x00000000 (before vmalloc)
abrooks
 cow.bitmap = 0xa2800000 (after vmalloc)
ubd_open enter
 Attempting to vmalloc COW bitmap \"cow0\" at 25600
cow.bitmap =
 0xa2800000 (before vmalloc)
cow.bitmap = 0xa280a000 (after
 vmalloc)
ubd_open exit
 /dev/ubd/disc0: p1
abrooks
 ubd_close() enter
ubd_close() exit
ubd_close()
 enter
ubd_close() exit
ubd_add exit

				Jeff


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Re: [uml-devel] many cow files with ubd_kern.c

[James McMechan]

Humm, I will look to see if that happens on my machines, nope
I just tested on a machine with more real memory but no skas3 no tmpfs I 
appear to have ~64M in use with one COW bitmap and 140M in use with 2 (from 
top in guest) the
other machine was shrinking the guest virtual address space to ~128M even 
when told to use 384M and the tmp(on tmpfs) was remounted with 
-oremount,size=10G

Though come to think of it the guest does not really need to have the 
vmalloced space
actually allocated with the backing file on tmp... but I can't think of a 
way to have it just mapped into high memory or something, but that would 
really be the place to put the 600M of bitmaps I expect to have if I can get 
things working.


>From: Jeff Dike <jdike@addtoit.com>
>To: James McMechan <james_mcmechan@hotmail.com>
>CC: user-mode-linux-devel@lists.sourceforge.net
>Subject: Re: [uml-devel] many cow files with ubd_kern.c
>Date: Sat, 28 Jan 2006 21:46:20 -0500
>
>On Sat, Jan 28, 2006 at 11:11:31PM +0000, James McMechan wrote:
> > allocation failed: out of vmalloc space - use "vmalloc=<size>" to 
>increse
> > size
> > Failed to vmalloc COW bitmap
> > ubd0: Can't open "COW0": errno -12
>
>I have a report (which I haven't looked into yet) of the ubd driver
>double-vmallocing the bitmap.  This is the call trace of the vmallocs
>as reported on IRC:
>
>ubd_add
>  enter
>Attempting to vmalloc COW bitmap \"cow0\" at
>  25600
>cow.bitmap = 0x00000000 (before vmalloc)
>abrooks
>  cow.bitmap = 0xa2800000 (after vmalloc)
>ubd_open enter
>  Attempting to vmalloc COW bitmap \"cow0\" at 25600
>cow.bitmap =
>  0xa2800000 (before vmalloc)
>cow.bitmap = 0xa280a000 (after
>  vmalloc)
>ubd_open exit
>  /dev/ubd/disc0: p1
>abrooks
>  ubd_close() enter
>ubd_close() exit
>ubd_close()
>  enter
>ubd_close() exit
>ubd_add exit
>
>				Jeff




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