In the case of using indirect, indirect desc must be allocated and released each time, which increases a lot of cpu overhead.
Here, a cache is added for indirect. If the number of indirect desc to be applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. Signed-off-by: Xuan Zhuo <[email protected]> --- drivers/virtio/virtio_ring.c | 57 +++++++++++++++++++++++++++++++----- 1 file changed, 49 insertions(+), 8 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 0b9a8544b0e8..4fd7bd5bcd70 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1074,10 +1074,45 @@ static void vring_unmap_desc_packed(const struct vring_virtqueue *vq, } } -static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg, +static void desc_cache_chain_free_packed(void *chain) +{ + struct vring_packed_desc *desc; + + while (chain) { + desc = chain; + chain = (void *)desc->addr; + kfree(desc); + } +} + +static void desc_cache_put_packed(struct vring_virtqueue *vq, + struct vring_packed_desc *desc, int n) +{ + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { + desc->addr = (u64)vq->desc_cache_chain; + vq->desc_cache_chain = desc; + } else { + kfree(desc); + } +} + +static struct vring_packed_desc *alloc_indirect_packed(struct vring_virtqueue *vq, + unsigned int total_sg, gfp_t gfp) { struct vring_packed_desc *desc; + unsigned int n; + + if (vq->use_desc_cache && total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) { + if (vq->desc_cache_chain) { + desc = vq->desc_cache_chain; + vq->desc_cache_chain = (void *)desc->addr; + return desc; + } + n = VIRT_QUEUE_CACHE_DESC_NUM; + } else { + n = total_sg; + } /* * We require lowmem mappings for the descriptors because @@ -1086,7 +1121,7 @@ static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg, */ gfp &= ~__GFP_HIGHMEM; - desc = kmalloc_array(total_sg, sizeof(struct vring_packed_desc), gfp); + desc = kmalloc_array(n, sizeof(struct vring_packed_desc), gfp); return desc; } @@ -1106,7 +1141,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, dma_addr_t addr; head = vq->packed.next_avail_idx; - desc = alloc_indirect_packed(total_sg, gfp); + desc = alloc_indirect_packed(vq, total_sg, gfp); if (unlikely(vq->vq.num_free < 1)) { pr_debug("Can't add buf len 1 - avail = 0\n"); @@ -1197,7 +1232,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, for (i = 0; i < err_idx; i++) vring_unmap_desc_packed(vq, &desc[i]); - kfree(desc); + desc_cache_put_packed(vq, desc, total_sg); END_USE(vq); return -ENOMEM; @@ -1422,20 +1457,22 @@ static void detach_buf_packed(struct vring_virtqueue *vq, } if (vq->indirect) { - u32 len; + u32 len, n; /* Free the indirect table, if any, now that it's unmapped. */ desc = state->indir_desc; if (!desc) return; + n = len / sizeof(struct vring_packed_desc); + if (vq->use_dma_api) { len = vq->packed.desc_extra[id].len; - for (i = 0; i < len / sizeof(struct vring_packed_desc); - i++) + for (i = 0; i < n; i++) vring_unmap_desc_packed(vq, &desc[i]); } - kfree(desc); + + desc_cache_put_packed(vq, desc, n); state->indir_desc = NULL; } else if (ctx) { *ctx = state->indir_desc; @@ -1753,6 +1790,8 @@ static struct virtqueue *vring_create_virtqueue_packed( vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && !context; vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); + vq->desc_cache_chain = NULL; + vq->use_desc_cache = vdev->desc_cache; if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) vq->weak_barriers = false; @@ -2374,6 +2413,8 @@ void vring_del_virtqueue(struct virtqueue *_vq) kfree(vq->split.desc_state); kfree(vq->split.desc_extra); desc_cache_chain_free_split(vq->desc_cache_chain); + } else { + desc_cache_chain_free_packed(vq->desc_cache_chain); } kfree(vq); } -- 2.31.0 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
