On Thu, Oct 28, 2021 at 06:49:19PM +0800, Xuan Zhuo wrote: > If the VIRTIO_RING_F_INDIRECT_DESC negotiation succeeds, and the number > of sgs used for sending packets is greater than 1. We must constantly > call __kmalloc/kfree to allocate/release desc. > > In the case of extremely fast package delivery, the overhead cannot be > ignored: > > 27.46% [kernel] [k] virtqueue_add > 16.66% [kernel] [k] detach_buf_split > 16.51% [kernel] [k] virtnet_xsk_xmit > 14.04% [kernel] [k] virtqueue_add_outbuf > 5.18% [kernel] [k] __kmalloc > 4.08% [kernel] [k] kfree > 2.80% [kernel] [k] virtqueue_get_buf_ctx > 2.22% [kernel] [k] xsk_tx_peek_desc > 2.08% [kernel] [k] memset_erms > 0.83% [kernel] [k] virtqueue_kick_prepare > 0.76% [kernel] [k] virtnet_xsk_run > 0.62% [kernel] [k] __free_old_xmit_ptr > 0.60% [kernel] [k] vring_map_one_sg > 0.53% [kernel] [k] native_apic_mem_write > 0.46% [kernel] [k] sg_next > 0.43% [kernel] [k] sg_init_table > 0.41% [kernel] [k] kmalloc_slab > > Compared to not using virtio indirect cache, virtio-net can get a 16% > performance improvement when using indirect desc cache. > > In the test case, the CPU where the package is sent has reached 100%. > The following are the PPS in two cases: > > indirect desc cache | no cache > 3074658 | 2685132 > 3111866 | 2666118 > 3152527 | 2653632 > 3125867 | 2669820 > 3027147 | 2644464 > 3069211 | 2669777 > 3038522 | 2675645 > 3034507 | 2671302 > 3102257 | 2685504 > 3083712 | 2692800 > 3051771 | 2676928 > 3080684 | 2695040 > 3147816 | 2720876 > 3123887 | 2705492 > 3180963 | 2699520 > 3191579 | 2676480 > 3161670 | 2686272 > 3189768 | 2692588 > 3174272 | 2686692 > 3143434 | 2682416 > > Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> > --- > drivers/net/virtio_net.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 4ad25a8b0870..e1ade176ab46 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -31,6 +31,13 @@ module_param(csum, bool, 0444); > module_param(gso, bool, 0444); > module_param(napi_tx, bool, 0644); > > +/** > + * Because virtio desc cache will increase memory overhead, users can turn it > + * off or select an acceptable value. The maximum value is 2 + MAX_SKB_FRAGS. > + */ Maybe add code to validate it and cap it at acceptable values then. > +static u32 virtio_desc_cache_thr = 4; Wouldn't something like CACHE_LINE_SIZE make more sense here? > +module_param(virtio_desc_cache_thr, uint, 0644); > + > /* FIXME: MTU in config. */ > #define GOOD_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN) > #define GOOD_COPY_LEN 128 > @@ -3214,6 +3221,11 @@ static int virtnet_probe(struct virtio_device *vdev) > vi->curr_queue_pairs = num_online_cpus(); > vi->max_queue_pairs = max_queue_pairs; > > + if (virtio_desc_cache_thr > 2 + MAX_SKB_FRAGS) > + virtio_set_desc_cache(vdev, 2 + MAX_SKB_FRAGS); > + else > + virtio_set_desc_cache(vdev, virtio_desc_cache_thr); > + > /* Allocate/initialize the rx/tx queues, and invoke find_vqs */ > err = init_vqs(vi); > if (err) > -- > 2.31.0 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
