[Crash-utility] enhance bt command

[Ming Zhang]

On Mon, 2008-03-03 at 14:04 -0500, Dave Anderson wrote:
> Ming Zhang wrote:
> 
> > my English sucks...
> > 
> > this is what i got. my side size-512 or size-1024 also works. just stuff
> > like dentry cache or inode cache does not work.
> > 
> > 
> > crash> rd 10078b2bca0 2
> >      10078b2bca0:  000001007877c8d4 00000100710fd5c8   ..wx.......q....
> > crash> rd -S 10078b2bca0 2
> >      10078b2bca0:  [dentry_cache]   00000100710fd5c8 
> > crash> kmem -s 10078b2bca0
> > kmem: address is not allocated in slab subsystem: 10078b2bca0
> 
> No, your English is fine -- it's your command-entering that sucks!
> 
> Above, when you entered "kmem -s 10078b2bca0", you're incorrectly entering
> the *address* where the dentry_cache reference (1007877c8d4) is located.
> And so it's telling you that 10078b2bca0 is not allocated in the slab
> subsystem, which it isn't...
> 
> But if you entered "kmem -s 1007877c8d4", you'd see the dentry_cache
> information.

yes. i noticed that. need some tea when handling 3 bugs at the same
time...

so here is my understanding. it actually shows the slab object that
contain that address. it might not be the address of that object. so
here is what i need to do

crash> rd -x 10078b2bca0
     10078b2bca0:  000001007877c8d4 
crash> rd -S 10078b2bca0
     10078b2bca0:  [dentry_cache]   

crash> kmem -s 000001007877c8d4
CACHE            NAME                 OBJSIZE  ALLOCATED     TOTAL
SLABS  SSIZE
10037ffc080      dentry_cache             240       9429     10560
660     4k
SLAB              MEMORY            TOTAL  ALLOCATED  FREE
1007877c040       1007877c088          16          9     7
FREE / [ALLOCATED]
  [1007877c8d4]

this only tell me that it belongs to one dentry object, but no idea
which one

then i have to use kmem -S dentry_cache, find out this piece

SLAB              MEMORY            TOTAL  ALLOCATED  FREE
1007877c040       1007877c088          16          9     7
FREE / [ALLOCATED]
  [1007877c088]
  [1007877c178]
   1007877c268  (cpu 1 cache)
   1007877c358  (cpu 1 cache)
  [1007877c448]
   1007877c538  (cpu 1 cache)
  [1007877c628]
  [1007877c718]
  [1007877c808]
~~~~~~~~~~~~~~~~~~~~ then find out it is here.
  [1007877c8f8]
   1007877c9e8  (cpu 1 cache)
   1007877cad8  (cpu 1 cache)
  [1007877cbc8]
  [1007877ccb8]
   1007877cda8  (cpu 1 cache)
   1007877ce98  (cpu 1 cache)

then i know the object contain this address is 1007877c808.
then 

crash> dentry.d_iname
struct dentry {
  [0xcc] unsigned char d_iname[36];
}
crash> eval c808+cc
hexadecimal: c8d4  
    decimal: 51412  
      octal: 144324

show me that variable in stack actually is d_iname.

then can we have the output format as

     10078b2bca0:  [000001007877c808+cc: dentry_cache]   

so we know the object address, which slab it is in, and the offset,
(thus can derive the raw value), all in one shot?


Thanks!



> 
> Dave
> 
> 
> 
-- 
Ming Zhang


@#$%^ purging memory... (*!%
http://blackmagic02881.wordpress.com/
http://www.linkedin.com/in/blackmagic02881
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