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Date: Fri, 19 May 2023 13:04:02 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Yuwei Guan <ssawgyw@...il.com>
Cc: rppt@...nel.org, akpm@...ux-foundation.org, tsahu@...ux.ibm.com,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] memblock: Add flags and nid info in memblock debugfs
On 5/18/23 19:35, Yuwei Guan wrote:
> Anshuman Khandual <anshuman.khandual@....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@...il.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", ®->base, &end);
> + seq_printf(m, "%pa..%pa ", ®->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", ®->base, &end);
>>> + seq_printf(m, "%pa..%pa ", ®->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;
>>> }
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