Re: 答复: [外部邮件] Re: [PATCH][rdma-next] RDMA/erdma: Use NUMA-aware allocation for MTT tables

[Cheng Xu <chengyou@linux.alibaba.com>]

On 2/26/26 3:09 PM, Leon Romanovsky wrote:
> On Thu, Feb 26, 2026 at 09:50:00AM +0800, Cheng Xu wrote:
>>
>>
>> On 2/25/26 8:07 PM, Li,Rongqing(ACG CCN) wrote:
>>>
>>>>> On 2/25/26 4:51 PM, lirongqing wrote:
>>>>>> From: Li RongQing <lirongqing@baidu.com>
>>>>>>
>>>>>> Currently, MTT (Memory Translation Table) buffers are allocated
>>>>>> without NUMA awareness using kzalloc() and vzalloc(), which allocate
>>>>>> memory on the NUMA node of the calling CPU. This can lead to
>>>>>> cross-node memory access latencies if the erdma device is attached
>>>>>> to a different NUMA socket.
>>>>>>
>>>>>> Switch to kzalloc_node() and vzalloc_node() to ensure MTT buffers
>>>>>> are allocated on the local NUMA node of the PCIe device
>>>> (dev->attrs.numa_node).
>>>>>> This reduces latency for hardware access and improves performance.
>>>>>>
>>>>>> Signed-off-by: Li RongQing <lirongqing@baidu.com>
>>>>>> ---
>>>>>>  drivers/infiniband/hw/erdma/erdma_verbs.c | 4 ++--
>>>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>>
>>>>>
>>>>> Hi, Li RongQing,
>>>>>
>>>>> Thanks for the patch. However, I think it is better to keep the
>>>>> current behavior, for the following reasons:
>>>>>
>>>>> 1. This path is in the control plane, so allocating memory from a remote
>>>>>    NUMA node should not have a noticeable performance impact.
>>>>
>>>> If TLB Miss , or the internal cache misses , does the HCA need to query the MTT?
>>>>
>>
>> This is rarely happen in our chip.
> 
> So why do we need this patch? The xxx_node() functions are useful when you
> need to force allocation on a specific NUMA node. In most cases, a plain
> kmalloc() will allocate memory on the same node as 'struct erdma_dev *dev',
> which typically matches the PCI device's NUMA node.
> 

Thanks for the detailed explanation.

> Please avoid vague phrasing like 'potentially improves performance' in the
> commit message and responses. It adds no meaningful information.
> 

Got it. 


> Also, please remove the dev->attrs.numa_node caching from erdma and rely on
> dev_to_node() instead.

OK, I will fix this.

Thanks,
Cheng Xu

> 
> Thanks