Re: [PATCH] fs/resctrl: Allocate the RMID array with kvzalloc

[Jinjie Ruan]

在 2026/11/4 18:51, Ben Horgan 写道:
> Hi Jinjie,
> 
> On 04/11/2026 10:20, Jinjie Ruan wrote:
>> setup_rmid_lru_list() sizes rmid_ptrs[] by the whole RMID index space.
>> On x86 the index is the RMID, so the array stays small. On MPAM the
>> index space is the product of the PARTID and PMG ranges, and with a
>> large range the array is megabytes in size.
>>
>> kzalloc() needs a high-order page allocation for it, which fails once
>> memory is fragmented, and a size above KMALLOC_MAX_SIZE always fails.
>> resctrl then fails to mount.
>>
>> Use kvzalloc(), which falls back to vmalloc().
> 
> Yep, I ran into this too when experimenting with large PARTID counts on the FVP model. I have the
> same patch here [1] and plan to repost soon with some more related kmalloc to kvmalloc changes.

Hi Ben,

Sorry, next time before sending, I will carefully check the email list.
Thank you for the review.

> 
> [1] https://lore.kernel.org/lkml/20260911160608.1091121-1-ben.horgan@xxxxxxx/
> 
> Thanks,
> 
> Ben
> 
>>
>> Fixes: 6791e0ea3071 ("x86/resctrl: Access per-rmid structures by index")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
>> Cc: <stable@xxxxxxxxxxxxxxx> # 7.1.x
>> Cc: Tony Luck <tony.luck@xxxxxxxxx>
>> Cc: Reinette Chatre <reinette.chatre@xxxxxxxxx>
>> Cc: Dave Martin <Dave.Martin@xxxxxxx>
>> Cc: James Morse <james.morse@xxxxxxx>
>> Cc: Babu Moger <babu.moger@xxxxxxx>
>> ---
>>  fs/resctrl/monitor.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/resctrl/monitor.c b/fs/resctrl/monitor.c
>> index f69dbf66f42e..7713aa5d3996 100644
>> --- a/fs/resctrl/monitor.c
>> +++ b/fs/resctrl/monitor.c
>> @@ -1029,7 +1029,7 @@ int setup_rmid_lru_list(void)
>>  		return 0;
>>  
>>  	idx_limit = resctrl_arch_system_num_rmid_idx();
>> -	rmid_ptrs = kzalloc_objs(struct rmid_entry, idx_limit);
>> +	rmid_ptrs = kvzalloc_objs(struct rmid_entry, idx_limit);
>>  	if (!rmid_ptrs)
>>  		return -ENOMEM;
>>  
>> @@ -1125,7 +1125,7 @@ void free_rmid_lru_list(void)
>>  		return;
>>  
>>  	mutex_lock(&rdtgroup_mutex);
>> -	kfree(rmid_ptrs);
>> +	kvfree(rmid_ptrs);
>>  	rmid_ptrs = NULL;
>>  	mutex_unlock(&rdtgroup_mutex);
>>  }
> 

-- 
Best regards,
Jinjie