Re: [PATCH v3 5/5] vhost_user: Increase number of memory regions

[fengchengwen <fengchengwen@huawei.com>]

On 11/11/2025 7:34 PM, Bathija, Pravin wrote:
> Responses inline.
> 
> 
> Internal Use - Confidential
>> -----Original Message-----
>> From: fengchengwen <fengchengwen@huawei.com>
>> Sent: Tuesday, November 4, 2025 12:12 AM
>> To: Bathija, Pravin <Pravin.Bathija@dell.com>; dev@dpdk.org
>> Cc: pravin.m.bathija.dev@gmail.com
>> Subject: Re: [PATCH v3 5/5] vhost_user: Increase number of memory regions
>>
>>
>> [EXTERNAL EMAIL]
>>
>> On 11/4/2025 12:21 PM, Pravin M Bathija wrote:
>>> In this patch the number of memory regions are increased from
>>> 8 to 128. When a vhost-user front-end such as qemu or libblkio queries
>>> the back-end such as dpdk with the message, get max number of memory
>>> slots, the back-end replies with this number 128 instead of the
>>> previously defined 8. The back-end also allocates that many slots in
>>> the memory table where regions are added/removed as requested by the
>>> vhost-user front-end. This also helps the vhost- user front-end to
>>> limit the number of memory regions when sending the set mem table
>>> message ar adding memory regions.
>>>
>>> Signed-off-by: Pravin M Bathija <pravin.bathija@dell.com>
>>> ---
>>>  lib/vhost/vhost_user.h | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/lib/vhost/vhost_user.h b/lib/vhost/vhost_user.h index
>>> 5a0e747b58..c6ad5b76d6 100644
>>> --- a/lib/vhost/vhost_user.h
>>> +++ b/lib/vhost/vhost_user.h
>>> @@ -11,7 +11,7 @@
>>>
>>>  /* refer to hw/virtio/vhost-user.c */
>>>
>>> -#define VHOST_MEMORY_MAX_NREGIONS 8
>>> +#define VHOST_MEMORY_MAX_NREGIONS 128
>>
>> The address translation may increase a lot if the real region is 128.
>> Maybe we should add another patch to optimize it.
> 
> Could you please share more thoughts on this ?  Are you concerned about the number of addresses and translation table bloat ? What optimization are you suggesting ?

Because each memory region is independent and does not overlap, maybe
we could use binary search to optimize it.

> 
>>
>>>
>>>  #define VHOST_USER_NET_SUPPORTED_FEATURES \
>>>     (VIRTIO_NET_SUPPORTED_FEATURES | \
> 
>