* [PATCH v3 1/3] virtio: cache indirect desc for split
2021-10-29 6:28 [PATCH v3 0/3] virtio support cache indirect desc Xuan Zhuo
@ 2021-10-29 6:28 ` Xuan Zhuo
2021-10-29 6:28 ` [PATCH v3 2/3] virtio: cache indirect desc for packed Xuan Zhuo
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Xuan Zhuo @ 2021-10-29 6:28 UTC (permalink / raw)
To: virtualization, netdev
Cc: Michael S. Tsirkin, Jason Wang, David S. Miller, Jakub Kicinski
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 <xuanzhuo@linux.alibaba.com>
---
drivers/virtio/virtio.c | 6 ++
drivers/virtio/virtio_ring.c | 105 ++++++++++++++++++++++++++++++++---
include/linux/virtio.h | 14 +++++
3 files changed, 117 insertions(+), 8 deletions(-)
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 0a5b54034d4b..1047149ac2a4 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev)
}
EXPORT_SYMBOL_GPL(is_virtio_device);
+void virtio_set_desc_cache(struct virtio_device *dev, u32 thr)
+{
+ dev->desc_cache_thr = thr;
+}
+EXPORT_SYMBOL_GPL(virtio_set_desc_cache);
+
void unregister_virtio_device(struct virtio_device *dev)
{
int index = dev->index; /* save for after device release */
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index dd95dfd85e98..010c47baa37f 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 thr;
+};
+
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 +438,76 @@ 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_free(struct vring_virtqueue *vq)
+{
+ kfree(vq->desc_cache.array);
+}
+
+static void desc_cache_create(struct vring_virtqueue *vq,
+ struct virtio_device *vdev, int size, int num)
+{
+ struct list_head *node;
+ int i;
+
+ BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct vring_desc));
+ BUILD_BUG_ON(sizeof(struct list_head) > sizeof(struct vring_packed_desc));
+
+ vq->desc_cache.array = NULL;
+ vq->desc_cache.thr = vdev->desc_cache_thr;
+
+ INIT_LIST_HEAD(&vq->desc_cache.list);
+
+ if (!vq->desc_cache.thr)
+ return;
+
+ size = size * vq->desc_cache.thr;
+
+ vq->desc_cache.array = kmalloc_array(num, size, GFP_KERNEL);
+ if (!vq->desc_cache.array) {
+ vq->desc_cache.thr = 0;
+ dev_warn(&vdev->dev, "queue[%d] alloc desc cache fail. turn off it.\n",
+ vq->vq.index);
+ return;
+ }
+
+ for (i = 0; i < num; ++i) {
+ node = vq->desc_cache.array + (i * size);
+ list_add(node, &vq->desc_cache.list);
+ }
+}
+
+static void __desc_cache_put(struct vring_virtqueue *vq,
+ struct list_head *node, int n)
+{
+ if (n <= vq->desc_cache.thr)
+ 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.thr)
+ 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 +521,12 @@ 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 +592,7 @@ 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 +736,7 @@ 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 +801,7 @@ 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 +813,12 @@ 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 +2286,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
!context;
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+ desc_cache_create(vq, vdev, sizeof(struct vring_desc), vring.num);
+
if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
vq->weak_barriers = false;
@@ -2329,6 +2417,7 @@ 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);
}
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 41edbc01ffa4..bda6f9853e97 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -118,6 +118,7 @@ struct virtio_device {
struct list_head vqs;
u64 features;
void *priv;
+ u32 desc_cache_thr;
};
static inline struct virtio_device *dev_to_virtio(struct device *_dev)
@@ -130,6 +131,19 @@ int register_virtio_device(struct virtio_device *dev);
void unregister_virtio_device(struct virtio_device *dev);
bool is_virtio_device(struct device *dev);
+/**
+ * virtio_set_desc_cache - set virtio ring desc cache threshold
+ *
+ * virtio will cache the allocated indirect desc.
+ *
+ * This function must be called before find_vqs.
+ *
+ * @thr:
+ * 0 - disable desc cache
+ * > 0 - enable desc cache. As the threshold of the desc cache.
+ */
+void virtio_set_desc_cache(struct virtio_device *dev, u32 thr);
+
void virtio_break_device(struct virtio_device *dev);
void virtio_config_changed(struct virtio_device *dev);
--
2.31.0
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v3 2/3] virtio: cache indirect desc for packed
2021-10-29 6:28 [PATCH v3 0/3] virtio support cache indirect desc Xuan Zhuo
2021-10-29 6:28 ` [PATCH v3 1/3] virtio: cache indirect desc for split Xuan Zhuo
@ 2021-10-29 6:28 ` Xuan Zhuo
2021-10-29 6:28 ` [PATCH v3 3/3] virtio-net: enable virtio desc cache Xuan Zhuo
2022-01-06 12:28 ` [PATCH v3 0/3] virtio support cache indirect desc Michael S. Tsirkin
3 siblings, 0 replies; 6+ messages in thread
From: Xuan Zhuo @ 2021-10-29 6:28 UTC (permalink / raw)
To: virtualization, netdev
Cc: Michael S. Tsirkin, Jason Wang, David S. Miller, Jakub Kicinski
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 <xuanzhuo@linux.alibaba.com>
---
drivers/virtio/virtio_ring.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 010c47baa37f..d853a281fb43 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1118,7 +1118,11 @@ static void vring_unmap_desc_packed(const struct vring_virtqueue *vq,
}
}
-static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
+#define desc_cache_get_packed(vq, n, gfp) \
+ _desc_cache_get(vq, n, gfp, struct vring_packed_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;
@@ -1130,7 +1134,7 @@ 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 = desc_cache_get_packed(vq, total_sg, gfp);
return desc;
}
@@ -1150,7 +1154,7 @@ 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");
@@ -1241,7 +1245,7 @@ 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(vq, desc, total_sg);
END_USE(vq);
return -ENOMEM;
@@ -1466,20 +1470,22 @@ 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;
+ len = vq->packed.desc_extra[id].len;
+ 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(vq, desc, n);
state->indir_desc = NULL;
} else if (ctx) {
*ctx = state->indir_desc;
@@ -1798,6 +1804,8 @@ static struct virtqueue *vring_create_virtqueue_packed(
!context;
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
+ desc_cache_create(vq, vdev, sizeof(struct vring_packed_desc), num);
+
if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
vq->weak_barriers = false;
@@ -2417,8 +2425,8 @@ 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);
}
+ desc_cache_free(vq);
kfree(vq);
}
EXPORT_SYMBOL_GPL(vring_del_virtqueue);
--
2.31.0
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v3 3/3] virtio-net: enable virtio desc cache
2021-10-29 6:28 [PATCH v3 0/3] virtio support cache indirect desc Xuan Zhuo
2021-10-29 6:28 ` [PATCH v3 1/3] virtio: cache indirect desc for split Xuan Zhuo
2021-10-29 6:28 ` [PATCH v3 2/3] virtio: cache indirect desc for packed Xuan Zhuo
@ 2021-10-29 6:28 ` Xuan Zhuo
2022-01-06 12:28 ` [PATCH v3 0/3] virtio support cache indirect desc Michael S. Tsirkin
3 siblings, 0 replies; 6+ messages in thread
From: Xuan Zhuo @ 2021-10-29 6:28 UTC (permalink / raw)
To: virtualization, netdev
Cc: Michael S. Tsirkin, Jason Wang, David S. Miller, Jakub Kicinski
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 virtio 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@linux.alibaba.com>
---
drivers/net/virtio_net.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4ad25a8b0870..df2514281847 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -31,6 +31,12 @@ 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.
+ */
+static u32 virtio_desc_cache_thr = 4;
+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 +3220,11 @@ 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
^ permalink raw reply [flat|nested] 6+ messages in thread