On 10/11/2016 11:01 AM, Yuanhan Liu wrote:
> On Tue, Oct 11, 2016 at 09:45:27AM +0200, Maxime Coquelin wrote:
>> @@ -684,12 +699,12 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct
>> vring_desc *descs,
>> struct rte_mempool *mbuf_pool)
>> {
>> struct vring_desc *desc;
>> - uint64_t desc_addr;
>> + uint64_t desc_addr = 0;
>> uint32_t desc_avail, desc_offset;
>> uint32_t mbuf_avail, mbuf_offset;
>> uint32_t cpy_len;
>> struct rte_mbuf *cur = m, *prev = m;
>> - struct virtio_net_hdr *hdr;
>> + struct virtio_net_hdr *hdr = NULL;
>> /* A counter to avoid desc dead loop chain */
>> uint32_t nr_desc = 1;
>>
>> @@ -698,12 +713,14 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct
>> vring_desc *descs,
>> (desc->flags & VRING_DESC_F_INDIRECT))
>> return -1;
>>
>> - desc_addr = gpa_to_vva(dev, desc->addr);
>> - if (unlikely(!desc_addr))
>> - return -1;
>> + if (virtio_net_with_host_offload(dev)) {
>> + desc_addr = gpa_to_vva(dev, desc->addr);
>> + if (unlikely(!desc_addr))
>> + return -1;
>>
>> - hdr = (struct virtio_net_hdr *)((uintptr_t)desc_addr);
>> - rte_prefetch0(hdr);
>> + hdr = (struct virtio_net_hdr *)((uintptr_t)desc_addr);
>> + rte_prefetch0(hdr);
>> + }
>>
>> /*
>> * A virtio driver normally uses at least 2 desc buffers
>> @@ -720,18 +737,24 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct
>> vring_desc *descs,
>> if (unlikely(!desc_addr))
>> return -1;
>>
>> - rte_prefetch0((void *)(uintptr_t)desc_addr);
>> -
>> desc_offset = 0;
>> desc_avail = desc->len;
>> nr_desc += 1;
>> -
>> - PRINT_PACKET(dev, (uintptr_t)desc_addr, desc->len, 0);
>> } else {
>> + if (!desc_addr) {
>> + desc_addr = gpa_to_vva(dev, desc->addr);
>> + if (unlikely(!desc_addr))
>> + return -1;
>> + }
>> +
>
> I think this piece of code make things a bit complex. I think what you
> want to achieve is, besides saving hdr prefetch, to save one call to
> gpa_to_vva() for the non-ANY_LAYOUT case. Does that matter too much?
>
> How about just saving the hdr prefetch?
>
> if (virtio_net_with_host_offload(dev)) {
> hdr = (struct virtio_net_hdr *)((uintptr_t)desc_addr);
> rte_prefetch0(hdr);
> }
Oops, you reply slipped through the cracks...
You're right, it doesn't matter too much, the thing to avoid id
definitely the hdr prefetch and access.
I'm sending a v3 now.
Thanks,
Maxime
