[linux-mm-cc] compcache fills vmalloc memory

[Anderson Briglia]

ext Nitin Gupta wrote:
> On Tue, Feb 26, 2008 at 8:38 PM, John McCabe-Dansted <gmatht at gmail.com> wrote:
>> Hi, I get the following error:
>>   xp at 7.10:~/bin$ sudo modprobe loop
>>   FATAL: Error inserting loop
>>  (/lib/modules/2.6.22-14-generic/kernel/drivers/block/loop.ko): Cannot
>>  allocate memory
>>   xp at 7.10:~/bin$ sudo umount compcache
>>   umount: compcache: not found
>>   xp at 7.10:~/bin$ sudo rmmod compcache
>>   ERROR: Module compcache is in use
>>   xp at 7.10:~/bin$ sudo swapoff compcache
>>   swapoff: compcache: No such file or directory
>>   xp at 7.10:~/bin$ sudo swapoff /dev/compcache
>>   xp at 7.10:~/bin$ sudo modprobe loop
>>
>>  The following appears to be the line in the syslog relating to why
>>  loop wouldn't load:ko): Cannot allocate memory
>>  allocation failed: out of vmalloc space - use vmalloc=<size> to increase size
>>
>>  They syslog was also filled with errors like the following:
>>  Feb 26 21:09:06 ubuntu-xp kernel: [196046.926003] allocation failed:
>>  out of vmalloc space - use vmalloc=<size> to increase size.
>>  Feb 26 21:09:06 ubuntu-xp kernel: [196046.926009] compcache: Error
>>  allocating memory for compressed page: 20631, size=2893
>>  Feb 26 21:09:06 ubuntu-xp kernel: [196046.926015] Write-error on
>>  swap-device (254:0:165056)
>>  allocation failed: out of vmalloc space - use vmalloc=<size> to increase size.
>>  compcache: Error allocating memory for compressed page: 20632, size=3195
>>  Feb 26 22:37:36 ubuntu-xp kernel: [201352.547315] Write-error on
>>  swap-device (254:0:165064)
>>
>>  --
>>  John C. McCabe-Dansted
>>  PhD Student
>>  University of Western Australia
> 
> 
> This is a limitation of compcache - If kernel reserved virtual address
> space (vmalloc area) gets exhausted, it will throw out these error
> even if plenty of physical memory is available.
> 
> If you really want bigger compcache, you can try one of these:
> - As error message suggests, use "vmalloc=<size>" boot param to
> increase this area.
> - Use 2G/2G user/kernel split (default is 3G/1G) - I'm not sure how to do this.

You should configure this on kernel configuration and re-compile it. You can find this option under "Processor type and
features -> Memory split" menu.

> 
> Also, what size did you set for compcache? and amount of physical RAM?
> This info is missing from log you provided.
> 
> Thanks,
> Nitin
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