Re: [PATCH v3] memblock: Add flags and nid info in memblock debugfs

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 5/18/23 19:35, Yuwei Guan wrote:
> Anshuman Khandual <anshuman.khandual@arm.com> 于2023年5月18日周四 18:12写道：
>>
>>
>>
>> On 5/18/23 14:44, Yuwei Guan wrote:
>>> Currently, the memblock debugfs can display the count of memblock_type and
>>> the base and end of the reg. However, when memblock_mark_*() or
>>> memblock_set_node() is executed on some range, the information in the
>>> existing debugfs cannot make it clear why the address is not consecutive.
>>>
>>> For example,
>>> cat /sys/kernel/debug/memblock/memory
>>>    0: 0x0000000080000000..0x00000000901fffff
>>>    1: 0x0000000090200000..0x00000000905fffff
>>>    2: 0x0000000090600000..0x0000000092ffffff
>>>    3: 0x0000000093000000..0x00000000973fffff
>>>    4: 0x0000000097400000..0x00000000b71fffff
>>>    5: 0x00000000c0000000..0x00000000dfffffff
>>>    6: 0x00000000e2500000..0x00000000f87fffff
>>>    7: 0x00000000f8800000..0x00000000fa7fffff
>>>    8: 0x00000000fa800000..0x00000000fd3effff
>>>    9: 0x00000000fd3f0000..0x00000000fd3fefff
>>>   10: 0x00000000fd3ff000..0x00000000fd7fffff
>>>   11: 0x00000000fd800000..0x00000000fd901fff
>>>   12: 0x00000000fd902000..0x00000000fd909fff
>>>   13: 0x00000000fd90a000..0x00000000fd90bfff
>>>   14: 0x00000000fd90c000..0x00000000ffffffff
>>>   15: 0x0000000880000000..0x0000000affffffff
>>>
>>> So we can add flags and nid to this debugfs.
>>>
>>> For example,
>>> cat /sys/kernel/debug/memblock/memory
>>>    0: 0x0000000080000000..0x00000000901fffff     NONE    0
>>>    1: 0x0000000090200000..0x00000000905fffff    NOMAP    0
>>>    2: 0x0000000090600000..0x0000000092ffffff     NONE    0
>>>    3: 0x0000000093000000..0x00000000973fffff    NOMAP    0
>>>    4: 0x0000000097400000..0x00000000b71fffff     NONE    0
>>>    5: 0x00000000c0000000..0x00000000dfffffff     NONE    0
>>>    6: 0x00000000e2500000..0x00000000f87fffff     NONE    0
>>>    7: 0x00000000f8800000..0x00000000fa7fffff    NOMAP    0
>>>    8: 0x00000000fa800000..0x00000000fd3effff     NONE    0
>>>    9: 0x00000000fd3f0000..0x00000000fd3fefff    NOMAP    0
>>>   10: 0x00000000fd3ff000..0x00000000fd7fffff     NONE    0
>>>   11: 0x00000000fd800000..0x00000000fd901fff    NOMAP    0
>>>   12: 0x00000000fd902000..0x00000000fd909fff     NONE    0
>>>   13: 0x00000000fd90a000..0x00000000fd90bfff    NOMAP    0
>>>   14: 0x00000000fd90c000..0x00000000ffffffff     NONE    0
>>>   15: 0x0000000880000000..0x0000000affffffff     NONE    0
>>
>> Although, Mike had suggested to keep these flags print last, above
>> format looks good as well.
>>
>>>
>>> Signed-off-by: Yuwei Guan <ssawgyw@gmail.com>
>>> ---
>>> v3:
>>> - show string value for each memblock flag
>>> ---
>>>  mm/memblock.c | 12 +++++++++++-
>>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/mm/memblock.c b/mm/memblock.c
>>> index 511d4783dcf1..5fba53f98b2d 100644
>>> --- a/mm/memblock.c
>>> +++ b/mm/memblock.c
>>> @@ -2143,13 +2143,23 @@ static int memblock_debug_show(struct seq_file *m, void *private)
>>>       struct memblock_region *reg;
>>>       int i;
>>>       phys_addr_t end;
>>> +     static const char flagname[BITS_PER_LONG][8] = {
>>> +             [0 ... (BITS_PER_LONG-1)] = "?",
>>
>> Minor nit -
>>
>> Although checkpatch does not complain, should there be spaces between
>> the operator and operands e.g (BITS_PER_LONG - 1).
>>
>>> +
>>> +             [ilog2(MEMBLOCK_HOTPLUG)] = "HOTPLUG",
>>> +             [ilog2(MEMBLOCK_MIRROR)] = "MIRROR",
>>> +             [ilog2(MEMBLOCK_NOMAP)] = "NOMAP",
>>> +             [ilog2(MEMBLOCK_DRIVER_MANAGED)] = "DRV_MNG",
>>> +     };
>>
>> Also, BITS_PER_LONG sized array is really required here ? as there are
>> just four available memblock flags.
>>
> Hi Anshuman,
> The main reason to use BITS_PER_LONG is to reserve.
> If the flagname buffer is (ilog2(MEMBLOCK_DRIVER_MANAGED) + 1),
> memblock_flags adds a new attribute and does not add its name in debugfs,
> it will cause an overflow.

Agreed.

> But BITS_PER_LONG is too wasteful, so I implement a new solution.
> Please help to check it.
> 
>         struct memblock_type *type = m->private;
>         struct memblock_region *reg;
> -       int i;
> +       int i, j;
>         phys_addr_t end;
> +       static const char *flagname[] = {
> +               [ilog2(MEMBLOCK_HOTPLUG)] = "HOTPLUG",
> +               [ilog2(MEMBLOCK_MIRROR)] = "MIRROR",
> +               [ilog2(MEMBLOCK_NOMAP)] = "NOMAP",
> +               [ilog2(MEMBLOCK_DRIVER_MANAGED)] = "DRV_MNG",
> +       };
> 
>         for (i = 0; i < type->cnt; i++) {
>                 reg = &type->regions[i];
>                 end = reg->base + reg->size - 1;
> 
>                 seq_printf(m, "%4d: ", i);
> -               seq_printf(m, "%pa..%pa\n", &reg->base, &end);
> +               seq_printf(m, "%pa..%pa ", &reg->base, &end);
> +               seq_printf(m, "%4d ", memblock_get_region_node(reg));
> +               if (reg->flags) {
> +                       for (j = 0; j < ARRAY_SIZE(flagname); j++) {
> +                               if (reg->flags & (1U << j)) {
> +                                       seq_printf(m, "%s\n", flagname[j]);
> +                                       break;
> +                               }
> +                       }
> +                       if (j == ARRAY_SIZE(flagname))
> +                               seq_printf(m, "%s\n", "UNKNOWN");
> +               } else {
> +                       seq_printf(m, "%s\n", "NONE");
> +               }
>         }

Please move the static array outside, just before this function and
capture ARRAY_SIZE(flagname) in a local variable to make it compact.

Rest looks good.

>>>
>>>       for (i = 0; i < type->cnt; i++) {
>>>               reg = &type->regions[i];
>>>               end = reg->base + reg->size - 1;
>>>
>>>               seq_printf(m, "%4d: ", i);
>>> -             seq_printf(m, "%pa..%pa\n", &reg->base, &end);
>>> +             seq_printf(m, "%pa..%pa ", &reg->base, &end);
>>> +             seq_printf(m, "%8s ", reg->flags ? flagname[ilog2(reg->flags)] : "NONE");
>>> +             seq_printf(m, "%4d\n", memblock_get_region_node(reg));
>>>       }
>>>       return 0;
>>>  }