Re: [dpdk-dev] [PATCH v4 1/7] vhost: fix missing memory table NUMA realloc

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 6/18/21 6:34 AM, Xia, Chenbo wrote:
> Hi Maxime,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Thursday, June 17, 2021 11:38 PM
>> To: dev@dpdk.org; david.marchand@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
>> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>; stable@dpdk.org
>> Subject: [PATCH v4 1/7] vhost: fix missing memory table NUMA realloc
>>
>> When the guest allocates virtqueues on a different NUMA node
>> than the one the Vhost metadata are allocated, both the Vhost
>> device struct and the virtqueues struct are reallocated.
>>
>> However, reallocating the Vhost memory table was missing, which
>> likely causes iat least one cross-NUMA accesses for every burst
>> of packets.
> 
> 'at least' ?

yes.

>>
>> This patch reallocates this table on the same NUMA node as the
>> other metadata.
>>
>> Fixes: 552e8fd3d2b4 ("vhost: simplify memory regions handling")
>> Cc: stable@dpdk.org
>>
>> Reported-by: David Marchand <david.marchand@redhat.com>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>>  lib/vhost/vhost_user.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
>> index 8f0eba6412..031e3bfa2f 100644
>> --- a/lib/vhost/vhost_user.c
>> +++ b/lib/vhost/vhost_user.c
>> @@ -557,6 +557,9 @@ numa_realloc(struct virtio_net *dev, int index)
> 
> As we are realloc more things now, the comment above 'numa_realloc(XXX)'
> should also be changed like:
> 
> Reallocate related data structure to make them on the same numa node as
> the memory of vring descriptor.

Agree, I'll put this:

"
Reallocate virtio_dev, vhost_virtqueue and related data structures to
make them on the same numa node as the memory of vring descriptor.
"

Thanks,
Maxime

> Thanks,
> Chenbo
> 
>>  		goto out;
>>  	}
>>  	if (oldnode != newnode) {
>> +		struct rte_vhost_memory *old_mem;
>> +		ssize_t mem_size;
>> +
>>  		VHOST_LOG_CONFIG(INFO,
>>  			"reallocate dev from %d to %d node\n",
>>  			oldnode, newnode);
>> @@ -568,6 +571,18 @@ numa_realloc(struct virtio_net *dev, int index)
>>
>>  		memcpy(dev, old_dev, sizeof(*dev));
>>  		rte_free(old_dev);
>> +
>> +		mem_size = sizeof(struct rte_vhost_memory) +
>> +			sizeof(struct rte_vhost_mem_region) * dev->mem->nregions;
>> +		old_mem = dev->mem;
>> +		dev->mem = rte_malloc_socket(NULL, mem_size, 0, newnode);
>> +		if (!dev->mem) {
>> +			dev->mem = old_mem;
>> +			goto out;
>> +		}
>> +
>> +		memcpy(dev->mem, old_mem, mem_size);
>> +		rte_free(old_mem);
>>  	}
>>
>>  out:
>> --
>> 2.31.1
>