[microblaze-uclinux] debugging kernel resource problems

[Rod Campbell <rod@xxxxxxxxxxxxxxxxxx>]

Hi,

We have been using the 2.4 uClinux microblaze kernel for a few years.  I 
am starting to notice what appears to be system resource problems, but 
have not found a good way to get a handle on it.  I wonder if anyone has 
suggestions about how to monitor and quantify this?

The uClinux environment has 24 MBytes available.  The app running on our 
uClinux  box has increased in size due to feature additions - from 
around 100K bytes to around 200K.  Under normal circumstances the app 
and the file support daemons (for jffs2 and flatfsd) are the only things 
running.  There is not a lot of file I/O and the files are few and small 
(configuration files).  There have been no problems with this environment.

I have a debug version that I normally use during development that is 
about 25% bigger than the prod app (around 250K).  I also often run 
programs from the serial console and ftp/telnet to monitor the system 
and download new app versions.  Lately I have noticed that the uClinux 
system will sometimes freeze up when I perform other activity with the 
debug app running.   Often there are no messages on the serial console, 
but sometimes I see "kernel BUG at buffer.c:xxxx" or "kernel BUG at 
slab.c:xxxx".

I tried turning on kernel debugging code by adding options to 
uClinux-2.4.x/arch/microblaze/config.in, then selecting them during the 
make process.  This included:

 bool 'Debug kernel' CONFIG_DEBUG_KERNEL
 bool 'Debug kmalloc/kfree' CONFIG_DEBUG_MALLOC
 bool 'Debug slab' CONFIG_DEBUG_SLAB
 bool 'Debug stack oflow' CONFIG_DEBUG_STACKOVERFLOW
 bool 'Debug Highmem' CONFIG_DEBUG_HIGHMEM
 bool 'Debug Errors' CONFIG_DEBUG_ERRORS
 bool 'Add /proc/mem_map' CONFIG_MEM_MAP
 bool 'Debug spinlock (smp)' CONFIG_DEBUG_SPINLOCK
 bool 'Debug user' CONFIG_DEBUG_USER
 bool 'Debug frame pointer' CONFIG_FRAME_POINTER
 bool 'Debug I/O Virt' CONFIG_DEBUG_IOVIRT
 bool 'Debug Checking' CONFIG_CHECKING
 bool 'Verbose BUG msgs' CONFIG_DEBUG_BUGVERBOSE

When I turned all these on, the kernel image increased in size and I did 
see one change (cat /proc/slabinfo showed more columns), but I did not 
see any more diagnostic messages on the serial console when it booted up 
or when I caused the system to freeze. 

Do I need to add something extra to another file somewhere to enable 
some of these debug parameters when the kernel is compiled?  Is there 
something else I could do to get memory statistics out of the kernel to 
see if this really is a memory resource issue?  Any advice would be 
appreciated.

Thanks,
Rod Campbell    
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