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 desc_cache_thr, the desc array with the size of desc_cache_thr is fixed and cached for reuse. Signed-off-by: Xuan Zhuo <[email protected]> --- drivers/virtio/virtio_ring.c | 126 ++++++++++++++++++++++++++++++++--- include/linux/virtio.h | 17 +++++ 2 files changed, 135 insertions(+), 8 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index dd95dfd85e98..a4a91c497a83 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -85,6 +85,19 @@ struct vring_desc_extra { u16 next; /* The next desc state in a list. */ }; +struct vring_desc_cache { + /* desc cache chain */ + struct list_head list; + + void *array; + + /* desc cache threshold + * 0 - disable desc cache + * > 0 - enable desc cache. As the threshold of the desc cache. + */ + u32 threshold; +}; + struct vring_virtqueue { struct virtqueue vq; @@ -117,6 +130,8 @@ struct vring_virtqueue { /* Hint for event idx: already triggered no need to disable. */ bool event_triggered; + struct vring_desc_cache desc_cache; + union { /* Available for split ring */ struct { @@ -423,7 +438,50 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, return extra[i].next; } -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, +static void desc_cache_init(struct vring_virtqueue *vq) +{ + vq->desc_cache.array = NULL; + vq->desc_cache.threshold = 0; + INIT_LIST_HEAD(&vq->desc_cache.list); +} + +static void desc_cache_free(struct vring_virtqueue *vq) +{ + kfree(vq->desc_cache.array); +} + +static void __desc_cache_put(struct vring_virtqueue *vq, + struct list_head *node, int n) +{ + if (n <= vq->desc_cache.threshold) + list_add(node, &vq->desc_cache.list); + else + kfree(node); +} + +#define desc_cache_put(vq, desc, n) \ + __desc_cache_put(vq, (struct list_head *)desc, n) + +static void *desc_cache_get(struct vring_virtqueue *vq, + int size, int n, gfp_t gfp) +{ + struct list_head *node; + + if (n > vq->desc_cache.threshold) + return kmalloc_array(n, size, gfp); + + node = vq->desc_cache.list.next; + list_del(node); + return node; +} + +#define _desc_cache_get(vq, n, gfp, tp) \ + ((tp *)desc_cache_get(vq, (sizeof(tp)), n, gfp)) + +#define desc_cache_get_split(vq, n, gfp) \ + _desc_cache_get(vq, n, gfp, struct vring_desc) + +static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, unsigned int total_sg, gfp_t gfp) { @@ -437,12 +495,12 @@ static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, */ gfp &= ~__GFP_HIGHMEM; - desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); + desc = desc_cache_get_split(vq, total_sg, gfp); if (!desc) return NULL; for (i = 0; i < total_sg; i++) - desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1); + desc[i].next = cpu_to_virtio16(vq->vq.vdev, i + 1); return desc; } @@ -508,7 +566,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, head = vq->free_head; if (virtqueue_use_indirect(_vq, total_sg)) - desc = alloc_indirect_split(_vq, total_sg, gfp); + desc = alloc_indirect_split(vq, total_sg, gfp); else { desc = NULL; WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); @@ -652,7 +710,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, } if (indirect) - kfree(desc); + desc_cache_put(vq, desc, total_sg); END_USE(vq); return -ENOMEM; @@ -717,7 +775,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, if (vq->indirect) { struct vring_desc *indir_desc = vq->split.desc_state[head].indir_desc; - u32 len; + u32 len, n; /* Free the indirect table, if any, now that it's unmapped. */ if (!indir_desc) @@ -729,10 +787,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, VRING_DESC_F_INDIRECT)); BUG_ON(len == 0 || len % sizeof(struct vring_desc)); - for (j = 0; j < len / sizeof(struct vring_desc); j++) + n = len / sizeof(struct vring_desc); + + for (j = 0; j < n; j++) vring_unmap_one_split_indirect(vq, &indir_desc[j]); - kfree(indir_desc); + desc_cache_put(vq, indir_desc, n); vq->split.desc_state[head].indir_desc = NULL; } else if (ctx) { *ctx = vq->split.desc_state[head].indir_desc; @@ -2200,6 +2260,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, !context; vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); + desc_cache_init(vq); + if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) vq->weak_barriers = false; @@ -2329,6 +2391,7 @@ void vring_del_virtqueue(struct virtqueue *_vq) if (!vq->packed_ring) { kfree(vq->split.desc_state); kfree(vq->split.desc_extra); + desc_cache_free(vq); } kfree(vq); } @@ -2445,6 +2508,53 @@ dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq) } EXPORT_SYMBOL_GPL(virtqueue_get_used_addr); +int virtqueue_set_desc_cache(struct virtqueue *_vq, u32 threshold) +{ + struct vring_virtqueue *vq = to_vvq(_vq); + struct list_head *node; + int size, num, i; + + BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct vring_desc)); + BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct vring_packed_desc)); + + BUG_ON(!vq->we_own_ring); + + if (!vq->indirect) + return 0; + + vq->desc_cache.threshold = threshold; + + if (!threshold) + return 0; + + if (vq->packed_ring) { + size = sizeof(struct vring_packed_desc); + num = vq->packed.vring.num; + } else { + size = sizeof(struct vring_desc); + num = vq->split.vring.num; + } + + size = size * vq->desc_cache.threshold; + + vq->desc_cache.array = kmalloc_array(num, size, GFP_KERNEL); + if (!vq->desc_cache.array) { + vq->desc_cache.threshold = 0; + dev_warn(&vq->vq.vdev->dev, + "queue[%d] alloc desc cache fail. turn off it.\n", + vq->vq.index); + return -1; + } + + for (i = 0; i < num; ++i) { + node = vq->desc_cache.array + (i * size); + list_add(node, &vq->desc_cache.list); + } + + return 0; +} +EXPORT_SYMBOL_GPL(virtqueue_set_desc_cache); + /* Only available for split ring */ const struct vring *virtqueue_get_vring(struct virtqueue *vq) { diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 41edbc01ffa4..e24b2e90dd42 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -89,6 +89,23 @@ dma_addr_t virtqueue_get_desc_addr(struct virtqueue *vq); dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq); dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq); +/** + * virtqueue_set_desc_cache - set virtio ring desc cache threshold + * + * virtio will allocate ring.num desc arrays of size threshold in advance. If + * total_sg exceeds the threshold, use kmalloc/kfree allocation indirect desc, + * if total_sg is less than or equal to the threshold, use these pre-allocated + * desc arrays. + * + * This function must be called immediately after find_vqs and before device + * ready. + * + * @threshold: + * 0 - disable desc cache + * > 0 - enable desc cache. As the threshold of the desc cache. + */ +int virtqueue_set_desc_cache(struct virtqueue *_vq, u32 threshold); + /** * virtio_device - representation of a device using virtio * @index: unique position on the virtio bus -- 2.31.0 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
