[Crash-utility] [PATCH] display information about "struct page" on SPARSEMEM.

[Dave Anderson]

Dave Anderson wrote:
> Ken'ichi Ohmichi wrote:
> 
>> Hi Dave,
>>
>> This patch fixes the problem that the crash utility cannot display
>> "struct page" information about SPARSEMEM (not SPARSEMEM_EXTREME) 
>> properly.
>>
>> The symbol mem_section is defined as the pointer array in 
>> SPARSEMEM_EXTREME.
>> On the other hand, SPARSEMEM's one is defined as the array of structure
>> mem_section like the following:
>>
>> linux-2.6.23/mm/sparse.c:18L
>>   #ifdef CONFIG_SPARSEMEM_EXTREME
>>   struct mem_section *mem_section[NR_SECTION_ROOTS]
>>           ____cacheline_internodealigned_in_smp;
>>   #else
>>   struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
>>            ____cacheline_internodealigned_in_smp;
>>   #endif
>>   EXPORT_SYMBOL(mem_section);
>>
>> The crash utility considers SPARSEMEM's one to be the pointer array,
>> but it is wrong. This patch fixes it.
>>
> 
> Interesting, I've never seen this problem before on any
> SPARSEMEM kernels.  But perhaps the original contributor
> of this patch, and myself, have never run a kernel configured
> with CONFIG_SPARSEMEM (i.e., only with CONFIG_SPARSEMEM_EXTREME)?
> (I don't have any dumpfiles to check)

Hi Ken'ichi,

I take that back -- I do have several x86_64 RHEL5 dumpfiles, and
as I suspected, all of them are CONFIG_SPARSEMEM_EXTREME.  So it
appears that the CONFIG_SPARSEMEM configuration was never tested?

Also, when I was looking at your patch without the full context,
I did not see that the code already has an if-else for the two
configurations, and that you are only changing the CONFIG_SPARSEMEM
section.  Sorry for the confusion...

I appreciate your fixing this -- it's queued for the next release.

Thanks again,
   Dave


> 
> In any case, can you confirm that this patch work for both cases?
> In other words, there is a differentiation between the _EXTREME and
> the non-EXTREME cases in the crash utility.  Should the patch be an
> if-else situation?
> 
> Dave
> 
> 
> 
>> The following results are this patch effects.
>>
>> * Before applying this patch
>>  crash> kmem -p
>>    PAGE    PHYSICAL   MAPPING    INDEX CNT FLAGS
>>  100              0   -------    -----   0 0
>>  120           1000   -------    -----   0 0
>>  140           2000   -------    -----   0 0
>>  160           3000   -------    -----   0 0
>>  180           4000   -------    -----   0 0
>>  1a0           5000   -------    -----   0 0
>>  1c0           6000   -------    -----   0 0
>>  1e0           7000   -------    -----   0 0
>>  200           8000   -------    -----   0 0
>>  [snip]
>>  crash>
>>
>> * After applying this patch
>>  crash> kmem -p
>>    PAGE    PHYSICAL   MAPPING    INDEX CNT FLAGS
>>  c5000000         0   -------    -----   1 400
>>  c5000020      1000   -------    -----   1 400
>>  c5000040      2000   -------    -----   1 400
>>  c5000060      3000   -------    -----   1 400
>>  c5000080      4000   -------    -----   1 400
>>  c50000a0      5000   -------    -----   1 400
>>  c50000c0      6000   -------    -----   1 400
>>  c50000e0      7000   -------    -----   1 400
>>  c5000100      8000   -------    -----   0 80000
>>  [snip]
>>  crash>
>>
>>
>> Thanks
>> Ken'ichi Ohmichi
>>
>> ---
>> Signed-off-by: Ken'ichi Ohmichi <oomichi at mxs.nes.nec.co.jp>
>>
>> ---
>> diff -rpuN crash-4.0-4.8.org/memory.c crash-4.0-4.8/memory.c
>> --- crash-4.0-4.8.org/memory.c    2007-10-31 11:49:16.000000000 +0900
>> +++ crash-4.0-4.8/memory.c    2007-11-01 10:28:15.000000000 +0900
>> @@ -12229,7 +12229,9 @@ nr_to_section(ulong nr)
>>          addr = mem_sec[SECTION_NR_TO_ROOT(nr)] +              (nr & 
>> SECTION_ROOT_MASK()) * SIZE(mem_section);
>>      else
>> -        addr = mem_sec[0] + (nr & SECTION_ROOT_MASK()) * 
>> SIZE(mem_section);
>> +        addr = symbol_value("mem_section") +
>> +            (SECTIONS_PER_ROOT() * SECTION_NR_TO_ROOT(nr) +
>> +            (nr & SECTION_ROOT_MASK())) * SIZE(mem_section);
>>  
>>      if (!IS_KVADDR(addr))
>>          return 0;
>> _
>>
>>
>>
>> -- 
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> 
> 
>