[dpdk-stable] [PATCH v4] examples/vhost: fix failure to launch dpdk-vhost

[Maxime Coquelin]

Hi Chenbo,

On 11/3/21 05:58, Xia, Chenbo wrote:
> Hi,
> 
>> -----Original Message-----
>> From: Ma, WenwuX <wenwux.ma at intel.com>
>> Sent: Wednesday, November 3, 2021 10:17 PM
>> To: dev at dpdk.org
>> Cc: maxime.coquelin at redhat.com; Xia, Chenbo <chenbo.xia at intel.com>; Yigit,
>> Ferruh <ferruh.yigit at intel.com>; Jiang, Cheng1 <cheng1.jiang at intel.com>; Hu,
>> Jiayu <jiayu.hu at intel.com>; Yang, YvonneX <yvonnex.yang at intel.com>; Ma, WenwuX
>> <wenwux.ma at intel.com>; stable at dpdk.org
>> Subject: [PATCH v4] examples/vhost: fix failure to launch dpdk-vhost
>>
>> When the default max queue value of vhost is 128, dpdk-vhost will fail to
>> launch with a 40G i40e port due to the mbuf allocation of the port queue fails.
>> Therefore, we modify the default value of max queue from 128 to 512,
>> it will ensure that there are enough mbufs.
>>
>> Fixes: 4796ad63ba1f ("examples/vhost: import userspace vhost application")
>> Cc: stable at dpdk.org
> 
> When I was tracking the bad commit, I notice this change is on purpose to save hugepages:
> 
> commit f17eb179046962fdc29c3609b1c9bd46bfefa4f5
> Author: Bernard Iremonger <bernard.iremonger at intel.com>
> Date:   Thu Dec 10 15:49:17 2015 +0000
> 
>      examples/vhost: reduce number of hugepages needed
> 
>      Add #ifndef MAX_QUEUES to change MAX_QUEUES at compile time if needed.
>      Change MAX_QUEUES from 512 to 128 to reduce the number of hugepages
>      required by the vhost-switch program.
> 
>      To change MAX_QUEUES add '-D MAX_QUEUES=512' to the EXTRA_CFLAGS variable,
>      before building the application.
> 
>      Signed-off-by: Bernard Iremonger <bernard.iremonger at intel.com>
>      Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
> 
> So as there's a way to solve the problem (although not perfect), I would suggest
> using the compiler flag to do tests with the specific NIC.
> 
> If no one has objection, let's drop the patch.

I agree, let's drop it.

Thanks,
Maxime
> Thanks,
> Chenbo
> 
>>
>> Signed-off-by: Wenwu Ma <wenwux.ma at intel.com>
>> Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
>> ---
>>   examples/vhost/main.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/examples/vhost/main.c b/examples/vhost/main.c
>> index bc3d71c898..36969a4de5 100644
>> --- a/examples/vhost/main.c
>> +++ b/examples/vhost/main.c
>> @@ -29,7 +29,7 @@
>>   #include "main.h"
>>
>>   #ifndef MAX_QUEUES
>> -#define MAX_QUEUES 128
>> +#define MAX_QUEUES 512
>>   #endif
>>
>>   /* the maximum number of external ports supported */
>> --
>> 2.25.1
>