>> Why does "page allocation failure" occur whereas there are still "58*4096kB
>> (C)"(*I think it indicates there are 58 order 10 memory could be used*)
>> could be used?
>>
>> Here is the related log:
>>
>> [ 2161.623563] xxxx: page allocation failure: order:10,
>> mode:0x2084020(GFP_ATOMIC|__GFP_COMP)
>
>If you look at the source for alloc_ap_req(), you find it wants GFP_ATOMIC, not
>CMA. And your box is fresh out of contiguous order-10 spaces that aren't CMA,
>and you're down to your last 3 order-9 flagged as (UEC).
>> (C)"(*I think it indicates there are 58 order 10 memory could be used*)
>> could be used?
>>
>> Here is the related log:
>>
>> [ 2161.623563] xxxx: page allocation failure: order:10,
>> mode:0x2084020(GFP_ATOMIC|__GFP_COMP)
>
>If you look at the source for alloc_ap_req(), you find it wants GFP_ATOMIC, not
>CMA. And your box is fresh out of contiguous order-10 spaces that aren't CMA,
>and you're down to your last 3 order-9 flagged as (UEC).
Thank you for the clarification.
I understand it on a deeper level with your help.
Why doesn't the kernel use two memory blocks whose size is 2048KB(i.e.oder 9 )
instead of one block order 10 (you see, there are still three free blocks and
2048KB*2=4096KB equivalent to the memory size of order 10)?
>If you look at the source for alloc_ap_req(), you find it wants GFP_ATOMIC, not
>CMA.
>CMA.
I followed your advice and read the related source code carefully.
It's corresponding to the log(i.e. mode:0x2084020(GFP_ATOMIC|__GFP_COMP) ).
Thank you for your attention to this matter.
Look forward to hearing from you.
Best regards.
Valdis Klētnieks <valdis.kletnieks@xxxxxx> 于2020年6月19日周五 下午12:48写道：
On Thu, 18 Jun 2020 14:21:05 +0800, sunshiong said:
> Why does "page allocation failure" occur whereas there are still "58*4096kB
> (C)"(*I think it indicates there are 58 order 10 memory could be used*)
> could be used?
>
> Here is the related log:
>
> [ 2161.623563] xxxx: page allocation failure: order:10,
> mode:0x2084020(GFP_ATOMIC|__GFP_COMP)
Most likely, the allocation wanted some other type of allocation.
The (C) on the order-10 says it's an CMA area.
static const char types[MIGRATE_TYPES] = {
[MIGRATE_UNMOVABLE] = 'U',
[MIGRATE_MOVABLE] = 'M',
[MIGRATE_RECLAIMABLE] = 'E',
[MIGRATE_HIGHATOMIC] = 'H',
#ifdef CONFIG_CMA
[MIGRATE_CMA] = 'C',
#endif
#ifdef CONFIG_MEMORY_ISOLATION
[MIGRATE_ISOLATE] = 'I',
#endif
If the call was for an unmovable, movable, reclaimable, or highatomic
allocation, you lose.
If you look at the source for alloc_ap_req(), you find it wants GFP_ATOMIC, not
CMA. And your box is fresh out of contiguous order-10 spaces that aren't CMA,
and you're down to your last 3 order-9 flagged as (UEC).
I admit I find it a tad suspicious that the USB gadget driver asks for a 4M
chunk of memory. Does USB actually support single transfers that large? (I'm
not a USB expert)
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
