[Crash-utility] [PATCH]: nr_node_ids

[Per Fransson]

On Fri, Sep 7, 2012 at 4:28 PM, Dave Anderson <anderson at redhat.com> wrote:
>
>
> ----- 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,

Hello =o)

>
> 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

Indeed, that's exactly what happened.

> 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;
>                         }

Again, indeed, that's more or less to the character what I changed it to.

>
> That looks reasonable to me.
>

Ok, because that was the main purpose of my first mail, understanding
whether there was a reason why the
'nr_node_ids'-has-been-turned-into-a-macro-case was treated as an
error in this context. So, you agree we could change it?

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

Nope, dead as a doornail. Are these messages to be expected then?

Oh, and sorry for putting "[PATCH]" in the title when there wasn't
one. It was by accident.

/Per

> Dave
>
>
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