[Crash-utility] [PATCH] Add -m option to kmem

[Dave Anderson]

----- Original Message -----

> > Well that adds a new angle, where the page structure address seems to
> > also be a logical "handle" -- in addition to the physical address
> > and stable_node address.  I would think that you would also want
> > to display the page-struct address as well.
> > 
> > I still don't understand why you want to restrict the optional
> > argument to a stable_node address, especially given that the page->mapping
> > "address" seen in "kmem -p" will have that extra 2-bit encoded into it,
> > so the user would have to remember to manually delete it when cutting-and-pasting
> > it from the "kmem -p" output.
> > 
> > Why not do what many of the other "kmem" options do, and allow the optional
> > argument to be either a page-struct address, a virtual address (of a
> > stable_node in this case), or a physical address?  Also you might want
> > to allow the user to enter the stable_node address directly from the
> > "kmem -p" output, and have the command strip the 2-bit off if the user
> > left it there.  (I think we do that kind of thing somewhere else...)
> > 
> 
> So the commandline may be:
> 
> crash > kmem -m [stable_node_addr | page_struct_addr | physical_addr]
> 
> the output may be:
> 
> >>
> >> STABLE_NODE     : <stable_node address>
> >> PAGE            : <page pointer address>
> >> PHYSICAL ADDRESS: <address>
> >>  
> >>             PID: 15864  MAPPING: 8713
> >>             VIRTUAL:
> >>             3639c1d000
> >>             3639c1e000
> >>             3639c1f000
> >>             ...

So in reality there would be 8713 virtual addresses dumped in the example above?

And taking it a step further, if for example, PID 15864 above were to
be a multi-threaded task with 100 threads, the same list of 8713 virtual
addresses would be re-displayed 100 times for each PID in the group? 

Clearly that would be way too much information for the command to be
of much help.  

Perhaps you could do what the "kmem -[fF]" and "kmem -[sS]" options do,
such that "kmem -m" would not display any virtual addresses, and "kmem -M"
would be the verbose option that does show them all.

And in the case of mulithreaded tasks, perhaps you could collaborate all
of the PID's in a list headed by the thread group leader prior to dumping
the virtual page list, i.e., maybe something like:

            PID: 15864  MAPPING: 8713  [thread group leader]
            PID: 15865
            PID: 15866
            PID: 15867
            VIRTUAL:
            3639c1d000
            3639c1e000
            3639c1f000
            ...
  
Dave