[Crash-utility] [PATCH]: nr_node_ids

[Dave Anderson]

----- Original Message -----
> Hi all,
> 
> I'm wondering about the use of the kernel 'nr_node_ids' variable in
> memory.c. In kmem_cache_downsize(), vt->kmem_cache_len_nodes defaults
> to 1 when 'nr_node_ids' isn't present. But in vm_init() an error
> message is printed in the same case. The reason I'm asking is that I'm
> getting that error
> 
>   "unable to initialize kmem slab cache subsystem"
> 
> on a 3.4 kernel. Having vm_init() default to
> 
>   vt->kmem_cache_len_nodes=1
> 
> as well seems to bring up the slab subsystem, although I'm getting a
> couple of
> 
>   "kmem: vm_area_struct: full list: slab: <nn1>  bad next pointer: <nn2>"
> 
> mixed into my kmem -S output. I have no idea if it's related.

Hi Per,

I don't have any recent sample kernels that have the configuration that your
kernel is running, so I can't confidently answer/test this.  I presume that
your kernel does not configure CONFIG_NODES_SHIFT (or set it to 0), so
that nr_node_ids becomes a #define instead of a variable.  And to get it
to work, I'm also presuming that you changed the "else" clause in vm_init()
to something like this:   

               if (MEMBER_TYPE("kmem_cache", "nodelists") == TYPE_CODE_PTR) {
                        int nr_node_ids;
                        /*
                         * nodelists now a pointer to an outside array
                         */
                        vt->flags |= NODELISTS_IS_PTR;
                        if (kernel_symbol_exists("nr_node_ids")) {
                                get_symbol_data("nr_node_ids", sizeof(int),
                                        &nr_node_ids);
                                vt->kmem_cache_len_nodes = nr_node_ids;
                        } else {
-                               error(INFO, "nr_node_ids: symbol does not exist\n");
-                               error(INFO, "unable to initialize kmem slab cache subsystem\n\n");
-                               vt->flags |= KMEM_CACHE_UNAVAIL;
+                               vt->kmem_cache_len_nodes = 1;
                        }

That looks reasonable to me.

As far as the "kmem -S" output, are you running it on a live system?

Dave