[dpdk-dev] [PATCH v2 0/3] vhost: make virtqueue cache-friendly

[dpdk-dev] [PATCH v2 0/3] vhost: make virtqueue cache-friendly

[Maxime Coquelin]

As done for Virtio PMD, this series improves cache utilization
of the vhost_virtqueue struct by removing unused field,
make the live-migration cache dynamically allocated at
live-migration setup time and by moving fields
around so that hot fields are on the first cachelines.

With this series, The struct vhost_virtqueue size goes
from 832B (13 cachelines) down to 320B (5 cachelines).

With this series and the virtio one, I measure a gain
of up to 8% in IO loop micro-benchmark with packed
ring, and 5% with split ring.

I don't have a setup at hand to run PVP testing, but
it might be interresting to get the numbers as I
suspect the cache pressure is higher in this test as
in real use-cases.

Changes in v2:
==============
- Add log_cache freeing in free_vq (Chenbo)

Maxime Coquelin (3):
  vhost: remove unused Vhost virtqueue field
  vhost: move dirty logging cache out of the virtqueue
  vhost: optimize vhost virtqueue struct

 lib/librte_vhost/vhost.c      | 16 +++++++++--
 lib/librte_vhost/vhost.h      | 54 +++++++++++++++++------------------
 lib/librte_vhost/vhost_user.c | 25 ++++++++++++++++
 3 files changed, 66 insertions(+), 29 deletions(-)

-- 
2.29.2

[dpdk-dev] [PATCH v2 1/3] vhost: remove unused Vhost virtqueue field

[Maxime Coquelin]

This patch removes the "backend" field of the
vhost_virtqueue struct, which is not used by the
library.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
---
 lib/librte_vhost/vhost.c | 2 --
 lib/librte_vhost/vhost.h | 2 --
 2 files changed, 4 deletions(-)

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 52ab93d1ec..5a7c0c6cff 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -558,8 +558,6 @@ init_vring_queue(struct virtio_net *dev, uint32_t vring_idx)
 	vq->notif_enable = VIRTIO_UNINITIALIZED_NOTIF;
 
 	vhost_user_iotlb_init(dev, vring_idx);
-	/* Backends are set to -1 indicating an inactive device. */
-	vq->backend = -1;
 }
 
 static void
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 658f6fc287..717f410548 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -143,8 +143,6 @@ struct vhost_virtqueue {
 #define VIRTIO_INVALID_EVENTFD		(-1)
 #define VIRTIO_UNINITIALIZED_EVENTFD	(-2)
 
-	/* Backend value to determine if device should started/stopped */
-	int			backend;
 	int			enabled;
 	int			access_ok;
 	int			ready;
-- 
2.29.2

[dpdk-dev] [PATCH v2 2/3] vhost: move dirty logging cache out of the virtqueue

[Maxime Coquelin]

This patch moves the per-virtqueue's dirty logging cache
out of the virtqueue struct, by allocating it dynamically
only when live-migration is enabled.

It saves 8 cachelines in vhost_virtqueue struct.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost.c      | 14 ++++++++++++++
 lib/librte_vhost/vhost.h      |  2 +-
 lib/librte_vhost/vhost_user.c | 25 +++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 5a7c0c6cff..c3490ce897 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -145,6 +145,10 @@ __vhost_log_cache_sync(struct virtio_net *dev, struct vhost_virtqueue *vq)
 	if (unlikely(!dev->log_base))
 		return;
 
+	/* No cache, nothing to sync */
+	if (unlikely(!vq->log_cache))
+		return;
+
 	rte_atomic_thread_fence(__ATOMIC_RELEASE);
 
 	log_base = (unsigned long *)(uintptr_t)dev->log_base;
@@ -177,6 +181,14 @@ vhost_log_cache_page(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	uint32_t offset = page / (sizeof(unsigned long) << 3);
 	int i;
 
+	if (unlikely(!vq->log_cache)) {
+		/* No logging cache allocated, write dirty log map directly */
+		rte_smp_wmb();
+		vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
+
+		return;
+	}
+
 	for (i = 0; i < vq->log_cache_nb_elem; i++) {
 		struct log_cache_entry *elem = vq->log_cache + i;
 
@@ -354,6 +366,8 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue *vq)
 	}
 	rte_free(vq->batch_copy_elems);
 	rte_mempool_free(vq->iotlb_pool);
+	if (vq->log_cache)
+		rte_free(vq->log_cache);
 	rte_free(vq);
 }
 
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 717f410548..3a71dfeed9 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -183,7 +183,7 @@ struct vhost_virtqueue {
 	bool			used_wrap_counter;
 	bool			avail_wrap_counter;
 
-	struct log_cache_entry log_cache[VHOST_LOG_CACHE_NR];
+	struct log_cache_entry *log_cache;
 	uint16_t log_cache_nb_elem;
 
 	rte_rwlock_t	iotlb_lock;
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index a60bb945ad..0f452d6ff3 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -2022,6 +2022,11 @@ vhost_user_get_vring_base(struct virtio_net **pdev,
 	rte_free(vq->batch_copy_elems);
 	vq->batch_copy_elems = NULL;
 
+	if (vq->log_cache) {
+		rte_free(vq->log_cache);
+		vq->log_cache = NULL;
+	}
+
 	msg->size = sizeof(msg->payload.state);
 	msg->fd_num = 0;
 
@@ -2121,6 +2126,7 @@ vhost_user_set_log_base(struct virtio_net **pdev, struct VhostUserMsg *msg,
 	int fd = msg->fds[0];
 	uint64_t size, off;
 	void *addr;
+	uint32_t i;
 
 	if (validate_msg_fds(msg, 1) != 0)
 		return RTE_VHOST_MSG_RESULT_ERR;
@@ -2174,6 +2180,25 @@ vhost_user_set_log_base(struct virtio_net **pdev, struct VhostUserMsg *msg,
 	dev->log_base = dev->log_addr + off;
 	dev->log_size = size;
 
+	for (i = 0; i < dev->nr_vring; i++) {
+		struct vhost_virtqueue *vq = dev->virtqueue[i];
+
+		if (vq->log_cache) {
+			rte_free(vq->log_cache);
+			vq->log_cache = NULL;
+		}
+		vq->log_cache_nb_elem = 0;
+		vq->log_cache = rte_zmalloc("vq log cache",
+				sizeof(struct log_cache_entry) * VHOST_LOG_CACHE_NR,
+				0);
+		/*
+		 * If log cache alloc fail, don't fail migration, but no
+		 * caching will be done, which will impact performance
+		 */
+		if (!vq->log_cache)
+			VHOST_LOG_CONFIG(ERR, "Failed to allocate VQ logging cache\n");
+	}
+
 	/*
 	 * The spec is not clear about it (yet), but QEMU doesn't expect
 	 * any payload in the reply.
-- 
2.29.2

[dpdk-dev] [PATCH v2 3/3] vhost: optimize vhost virtqueue struct

[Maxime Coquelin]

This patch moves vhost_virtuqueue struct fields in order
to both optimize packing and move hot fields on the first
cachelines.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/vhost.h | 52 +++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 25 deletions(-)

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 3a71dfeed9..ae45b05dd1 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -133,7 +133,7 @@ struct vhost_virtqueue {
 		struct vring_used	*used;
 		struct vring_packed_desc_event *device_event;
 	};
-	uint32_t		size;
+	uint16_t		size;
 
 	uint16_t		last_avail_idx;
 	uint16_t		last_used_idx;
@@ -143,29 +143,12 @@ struct vhost_virtqueue {
 #define VIRTIO_INVALID_EVENTFD		(-1)
 #define VIRTIO_UNINITIALIZED_EVENTFD	(-2)
 
-	int			enabled;
-	int			access_ok;
-	int			ready;
-	int			notif_enable;
-#define VIRTIO_UNINITIALIZED_NOTIF	(-1)
+	bool			enabled;
+	bool			access_ok;
+	bool			ready;
 
 	rte_spinlock_t		access_lock;
 
-	/* Used to notify the guest (trigger interrupt) */
-	int			callfd;
-	/* Currently unused as polling mode is enabled */
-	int			kickfd;
-
-	/* Physical address of used ring, for logging */
-	uint64_t		log_guest_addr;
-
-	/* inflight share memory info */
-	union {
-		struct rte_vhost_inflight_info_split *inflight_split;
-		struct rte_vhost_inflight_info_packed *inflight_packed;
-	};
-	struct rte_vhost_resubmit_info *resubmit_inflight;
-	uint64_t		global_counter;
 
 	union {
 		struct vring_used_elem  *shadow_used_split;
@@ -176,22 +159,36 @@ struct vhost_virtqueue {
 	uint16_t		shadow_aligned_idx;
 	/* Record packed ring first dequeue desc index */
 	uint16_t		shadow_last_used_idx;
-	struct vhost_vring_addr ring_addrs;
 
-	struct batch_copy_elem	*batch_copy_elems;
 	uint16_t		batch_copy_nb_elems;
+	struct batch_copy_elem	*batch_copy_elems;
 	bool			used_wrap_counter;
 	bool			avail_wrap_counter;
 
-	struct log_cache_entry *log_cache;
+	/* Physical address of used ring, for logging */
 	uint16_t log_cache_nb_elem;
+	uint64_t		log_guest_addr;
+	struct log_cache_entry *log_cache;
 
 	rte_rwlock_t	iotlb_lock;
 	rte_rwlock_t	iotlb_pending_lock;
 	struct rte_mempool *iotlb_pool;
 	TAILQ_HEAD(, vhost_iotlb_entry) iotlb_list;
-	int				iotlb_cache_nr;
 	TAILQ_HEAD(, vhost_iotlb_entry) iotlb_pending_list;
+	int				iotlb_cache_nr;
+
+	/* Used to notify the guest (trigger interrupt) */
+	int			callfd;
+	/* Currently unused as polling mode is enabled */
+	int			kickfd;
+
+	/* inflight share memory info */
+	union {
+		struct rte_vhost_inflight_info_split *inflight_split;
+		struct rte_vhost_inflight_info_packed *inflight_packed;
+	};
+	struct rte_vhost_resubmit_info *resubmit_inflight;
+	uint64_t		global_counter;
 
 	/* operation callbacks for async dma */
 	struct rte_vhost_async_channel_ops	async_ops;
@@ -212,6 +209,11 @@ struct vhost_virtqueue {
 	bool		async_inorder;
 	bool		async_registered;
 	uint16_t	async_threshold;
+
+	int			notif_enable;
+#define VIRTIO_UNINITIALIZED_NOTIF	(-1)
+
+	struct vhost_vring_addr ring_addrs;
 } __rte_cache_aligned;
 
 /* Virtio device status as per Virtio specification */
-- 
2.29.2

Re: [dpdk-dev] [PATCH v2 2/3] vhost: move dirty logging cache out of the virtqueue

[David Marchand]

On Tue, Mar 16, 2021 at 1:42 PM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
>
> This patch moves the per-virtqueue's dirty logging cache
> out of the virtqueue struct, by allocating it dynamically
> only when live-migration is enabled.
>
> It saves 8 cachelines in vhost_virtqueue struct.
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_vhost/vhost.c      | 14 ++++++++++++++
>  lib/librte_vhost/vhost.h      |  2 +-
>  lib/librte_vhost/vhost_user.c | 25 +++++++++++++++++++++++++
>  3 files changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
> index 5a7c0c6cff..c3490ce897 100644
> --- a/lib/librte_vhost/vhost.c
> +++ b/lib/librte_vhost/vhost.c
> @@ -145,6 +145,10 @@ __vhost_log_cache_sync(struct virtio_net *dev, struct vhost_virtqueue *vq)
>         if (unlikely(!dev->log_base))
>                 return;
>
> +       /* No cache, nothing to sync */
> +       if (unlikely(!vq->log_cache))
> +               return;
> +
>         rte_atomic_thread_fence(__ATOMIC_RELEASE);
>
>         log_base = (unsigned long *)(uintptr_t)dev->log_base;
> @@ -177,6 +181,14 @@ vhost_log_cache_page(struct virtio_net *dev, struct vhost_virtqueue *vq,
>         uint32_t offset = page / (sizeof(unsigned long) << 3);
>         int i;
>
> +       if (unlikely(!vq->log_cache)) {
> +               /* No logging cache allocated, write dirty log map directly */
> +               rte_smp_wmb();

We try not to reintroduce full barriers (checkpatch caught this).


> +               vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
> +
> +               return;
> +       }
> +
>         for (i = 0; i < vq->log_cache_nb_elem; i++) {
>                 struct log_cache_entry *elem = vq->log_cache + i;
>
> @@ -354,6 +366,8 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue *vq)
>         }
>         rte_free(vq->batch_copy_elems);
>         rte_mempool_free(vq->iotlb_pool);
> +       if (vq->log_cache)
> +               rte_free(vq->log_cache);

No if() needed.


>         rte_free(vq);
>  }
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 717f410548..3a71dfeed9 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -183,7 +183,7 @@ struct vhost_virtqueue {
>         bool                    used_wrap_counter;
>         bool                    avail_wrap_counter;
>
> -       struct log_cache_entry log_cache[VHOST_LOG_CACHE_NR];
> +       struct log_cache_entry *log_cache;
>         uint16_t log_cache_nb_elem;
>
>         rte_rwlock_t    iotlb_lock;
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index a60bb945ad..0f452d6ff3 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -2022,6 +2022,11 @@ vhost_user_get_vring_base(struct virtio_net **pdev,
>         rte_free(vq->batch_copy_elems);
>         vq->batch_copy_elems = NULL;
>
> +       if (vq->log_cache) {
> +               rte_free(vq->log_cache);
> +               vq->log_cache = NULL;
> +       }

Idem.


> +
>         msg->size = sizeof(msg->payload.state);
>         msg->fd_num = 0;
>
> @@ -2121,6 +2126,7 @@ vhost_user_set_log_base(struct virtio_net **pdev, struct VhostUserMsg *msg,
>         int fd = msg->fds[0];
>         uint64_t size, off;
>         void *addr;
> +       uint32_t i;
>
>         if (validate_msg_fds(msg, 1) != 0)
>                 return RTE_VHOST_MSG_RESULT_ERR;
> @@ -2174,6 +2180,25 @@ vhost_user_set_log_base(struct virtio_net **pdev, struct VhostUserMsg *msg,
>         dev->log_base = dev->log_addr + off;
>         dev->log_size = size;
>
> +       for (i = 0; i < dev->nr_vring; i++) {
> +               struct vhost_virtqueue *vq = dev->virtqueue[i];
> +
> +               if (vq->log_cache) {
> +                       rte_free(vq->log_cache);
> +                       vq->log_cache = NULL;
> +               }

Idem.


> +               vq->log_cache_nb_elem = 0;
> +               vq->log_cache = rte_zmalloc("vq log cache",
> +                               sizeof(struct log_cache_entry) * VHOST_LOG_CACHE_NR,
> +                               0);
> +               /*
> +                * If log cache alloc fail, don't fail migration, but no
> +                * caching will be done, which will impact performance
> +                */
> +               if (!vq->log_cache)
> +                       VHOST_LOG_CONFIG(ERR, "Failed to allocate VQ logging cache\n");
> +       }
> +
>         /*
>          * The spec is not clear about it (yet), but QEMU doesn't expect
>          * any payload in the reply.
> --
> 2.29.2
>


-- 
David Marchand

Re: [dpdk-dev] [PATCH v2 3/3] vhost: optimize vhost virtqueue struct

[David Marchand]

On Tue, Mar 16, 2021 at 1:42 PM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
>
> This patch moves vhost_virtuqueue struct fields in order

virtqueue
You might want to add something in your local dictionary :-p.


> to both optimize packing and move hot fields on the first
> cachelines.
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_vhost/vhost.h | 52 +++++++++++++++++++++-------------------
>  1 file changed, 27 insertions(+), 25 deletions(-)
>
> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
> index 3a71dfeed9..ae45b05dd1 100644
> --- a/lib/librte_vhost/vhost.h
> +++ b/lib/librte_vhost/vhost.h
> @@ -133,7 +133,7 @@ struct vhost_virtqueue {
>                 struct vring_used       *used;
>                 struct vring_packed_desc_event *device_event;
>         };
> -       uint32_t                size;
> +       uint16_t                size;

There is one site in the code that could be problematic:

vhost_user_set_vring_num()
...
vq->size = msg->payload.state.num;
...
if (vq->size > 32768) {

payload.state.num is an unsigned int, so we'd better check its value
as an unsigned int, before storing to vq->size.


>
>         uint16_t                last_avail_idx;
>         uint16_t                last_used_idx;
> @@ -143,29 +143,12 @@ struct vhost_virtqueue {
>  #define VIRTIO_INVALID_EVENTFD         (-1)
>  #define VIRTIO_UNINITIALIZED_EVENTFD   (-2)
>
> -       int                     enabled;
> -       int                     access_ok;
> -       int                     ready;
> -       int                     notif_enable;
> -#define VIRTIO_UNINITIALIZED_NOTIF     (-1)
> +       bool                    enabled;
> +       bool                    access_ok;
> +       bool                    ready;

Changing those types is fine, but it is a bit odd to still see
boolean_var = 0 or boolean_var = 1 in the rest of the code.


>
>         rte_spinlock_t          access_lock;
>
> -       /* Used to notify the guest (trigger interrupt) */
> -       int                     callfd;
> -       /* Currently unused as polling mode is enabled */
> -       int                     kickfd;
> -
> -       /* Physical address of used ring, for logging */
> -       uint64_t                log_guest_addr;
> -
> -       /* inflight share memory info */
> -       union {
> -               struct rte_vhost_inflight_info_split *inflight_split;
> -               struct rte_vhost_inflight_info_packed *inflight_packed;
> -       };
> -       struct rte_vhost_resubmit_info *resubmit_inflight;
> -       uint64_t                global_counter;
>
>         union {
>                 struct vring_used_elem  *shadow_used_split;
> @@ -176,22 +159,36 @@ struct vhost_virtqueue {
>         uint16_t                shadow_aligned_idx;
>         /* Record packed ring first dequeue desc index */
>         uint16_t                shadow_last_used_idx;
> -       struct vhost_vring_addr ring_addrs;
>
> -       struct batch_copy_elem  *batch_copy_elems;
>         uint16_t                batch_copy_nb_elems;
> +       struct batch_copy_elem  *batch_copy_elems;
>         bool                    used_wrap_counter;
>         bool                    avail_wrap_counter;
>
> -       struct log_cache_entry *log_cache;
> +       /* Physical address of used ring, for logging */
>         uint16_t log_cache_nb_elem;

Indent is broken / not consistent, probably because you cut/pasted lines.


> +       uint64_t                log_guest_addr;
> +       struct log_cache_entry *log_cache;
>
>         rte_rwlock_t    iotlb_lock;
>         rte_rwlock_t    iotlb_pending_lock;
>         struct rte_mempool *iotlb_pool;
>         TAILQ_HEAD(, vhost_iotlb_entry) iotlb_list;
> -       int                             iotlb_cache_nr;
>         TAILQ_HEAD(, vhost_iotlb_entry) iotlb_pending_list;
> +       int                             iotlb_cache_nr;
> +
> +       /* Used to notify the guest (trigger interrupt) */
> +       int                     callfd;
> +       /* Currently unused as polling mode is enabled */
> +       int                     kickfd;
> +
> +       /* inflight share memory info */
> +       union {
> +               struct rte_vhost_inflight_info_split *inflight_split;
> +               struct rte_vhost_inflight_info_packed *inflight_packed;
> +       };
> +       struct rte_vhost_resubmit_info *resubmit_inflight;
> +       uint64_t                global_counter;
>
>         /* operation callbacks for async dma */
>         struct rte_vhost_async_channel_ops      async_ops;
> @@ -212,6 +209,11 @@ struct vhost_virtqueue {
>         bool            async_inorder;
>         bool            async_registered;
>         uint16_t        async_threshold;
> +
> +       int                     notif_enable;
> +#define VIRTIO_UNINITIALIZED_NOTIF     (-1)
> +
> +       struct vhost_vring_addr ring_addrs;
>  } __rte_cache_aligned;
>
>  /* Virtio device status as per Virtio specification */
> --
> 2.29.2
>



-- 
David Marchand

Re: [dpdk-dev] [PATCH v2 2/3] vhost: move dirty logging cache out of the virtqueue

[Maxime Coquelin]

On 3/16/21 2:13 PM, David Marchand wrote:
> On Tue, Mar 16, 2021 at 1:42 PM Maxime Coquelin
> <maxime.coquelin@redhat.com> wrote:
>>
>> This patch moves the per-virtqueue's dirty logging cache
>> out of the virtqueue struct, by allocating it dynamically
>> only when live-migration is enabled.
>>
>> It saves 8 cachelines in vhost_virtqueue struct.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>>  lib/librte_vhost/vhost.c      | 14 ++++++++++++++
>>  lib/librte_vhost/vhost.h      |  2 +-
>>  lib/librte_vhost/vhost_user.c | 25 +++++++++++++++++++++++++
>>  3 files changed, 40 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
>> index 5a7c0c6cff..c3490ce897 100644
>> --- a/lib/librte_vhost/vhost.c
>> +++ b/lib/librte_vhost/vhost.c
>> @@ -145,6 +145,10 @@ __vhost_log_cache_sync(struct virtio_net *dev, struct vhost_virtqueue *vq)
>>         if (unlikely(!dev->log_base))
>>                 return;
>>
>> +       /* No cache, nothing to sync */
>> +       if (unlikely(!vq->log_cache))
>> +               return;
>> +
>>         rte_atomic_thread_fence(__ATOMIC_RELEASE);
>>
>>         log_base = (unsigned long *)(uintptr_t)dev->log_base;
>> @@ -177,6 +181,14 @@ vhost_log_cache_page(struct virtio_net *dev, struct vhost_virtqueue *vq,
>>         uint32_t offset = page / (sizeof(unsigned long) << 3);
>>         int i;
>>
>> +       if (unlikely(!vq->log_cache)) {
>> +               /* No logging cache allocated, write dirty log map directly */
>> +               rte_smp_wmb();
> 
> We try not to reintroduce full barriers (checkpatch caught this).

Agree, the rebase introduced it again silently.

> 
>> +               vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
>> +
>> +               return;
>> +       }
>> +
>>         for (i = 0; i < vq->log_cache_nb_elem; i++) {
>>                 struct log_cache_entry *elem = vq->log_cache + i;
>>
>> @@ -354,6 +366,8 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue *vq)
>>         }
>>         rte_free(vq->batch_copy_elems);
>>         rte_mempool_free(vq->iotlb_pool);
>> +       if (vq->log_cache)
>> +               rte_free(vq->log_cache);
> 
> No if() needed.

Yes, will fix in next revision.

> 
>>         rte_free(vq);
>>  }
>>
>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>> index 717f410548..3a71dfeed9 100644
>> --- a/lib/librte_vhost/vhost.h
>> +++ b/lib/librte_vhost/vhost.h
>> @@ -183,7 +183,7 @@ struct vhost_virtqueue {
>>         bool                    used_wrap_counter;
>>         bool                    avail_wrap_counter;
>>
>> -       struct log_cache_entry log_cache[VHOST_LOG_CACHE_NR];
>> +       struct log_cache_entry *log_cache;
>>         uint16_t log_cache_nb_elem;
>>
>>         rte_rwlock_t    iotlb_lock;
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index a60bb945ad..0f452d6ff3 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -2022,6 +2022,11 @@ vhost_user_get_vring_base(struct virtio_net **pdev,
>>         rte_free(vq->batch_copy_elems);
>>         vq->batch_copy_elems = NULL;
>>
>> +       if (vq->log_cache) {
>> +               rte_free(vq->log_cache);
>> +               vq->log_cache = NULL;
>> +       }
> 
> Idem.
> 
> 

Thanks,
Maxime

Re: [dpdk-dev] [PATCH v2 3/3] vhost: optimize vhost virtqueue struct

[Maxime Coquelin]

On 3/16/21 2:38 PM, David Marchand wrote:
> On Tue, Mar 16, 2021 at 1:42 PM Maxime Coquelin
> <maxime.coquelin@redhat.com> wrote:
>>
>> This patch moves vhost_virtuqueue struct fields in order
> 
> virtqueue
> You might want to add something in your local dictionary :-p.
> 
> 
>> to both optimize packing and move hot fields on the first
>> cachelines.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
>> ---
>>  lib/librte_vhost/vhost.h | 52 +++++++++++++++++++++-------------------
>>  1 file changed, 27 insertions(+), 25 deletions(-)
>>
>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>> index 3a71dfeed9..ae45b05dd1 100644
>> --- a/lib/librte_vhost/vhost.h
>> +++ b/lib/librte_vhost/vhost.h
>> @@ -133,7 +133,7 @@ struct vhost_virtqueue {
>>                 struct vring_used       *used;
>>                 struct vring_packed_desc_event *device_event;
>>         };
>> -       uint32_t                size;
>> +       uint16_t                size;
> 
> There is one site in the code that could be problematic:
> 
> vhost_user_set_vring_num()
> ...
> vq->size = msg->payload.state.num;
> ...
> if (vq->size > 32768) {
> 
> payload.state.num is an unsigned int, so we'd better check its value
> as an unsigned int, before storing to vq->size.

Indeed, I will rework the function, so that it checks that
msg->payload.state.num is smaller than 32K to comply with the spec,
and so remove the later check on vq->size.

> 
>>
>>         uint16_t                last_avail_idx;
>>         uint16_t                last_used_idx;
>> @@ -143,29 +143,12 @@ struct vhost_virtqueue {
>>  #define VIRTIO_INVALID_EVENTFD         (-1)
>>  #define VIRTIO_UNINITIALIZED_EVENTFD   (-2)
>>
>> -       int                     enabled;
>> -       int                     access_ok;
>> -       int                     ready;
>> -       int                     notif_enable;
>> -#define VIRTIO_UNINITIALIZED_NOTIF     (-1)
>> +       bool                    enabled;
>> +       bool                    access_ok;
>> +       bool                    ready;
> 
> Changing those types is fine, but it is a bit odd to still see
> boolean_var = 0 or boolean_var = 1 in the rest of the code.

Yes, I fix all the places with assigning boolean values.

> 
>>
>>         rte_spinlock_t          access_lock;
>>
>> -       /* Used to notify the guest (trigger interrupt) */
>> -       int                     callfd;
>> -       /* Currently unused as polling mode is enabled */
>> -       int                     kickfd;
>> -
>> -       /* Physical address of used ring, for logging */
>> -       uint64_t                log_guest_addr;
>> -
>> -       /* inflight share memory info */
>> -       union {
>> -               struct rte_vhost_inflight_info_split *inflight_split;
>> -               struct rte_vhost_inflight_info_packed *inflight_packed;
>> -       };
>> -       struct rte_vhost_resubmit_info *resubmit_inflight;
>> -       uint64_t                global_counter;
>>
>>         union {
>>                 struct vring_used_elem  *shadow_used_split;
>> @@ -176,22 +159,36 @@ struct vhost_virtqueue {
>>         uint16_t                shadow_aligned_idx;
>>         /* Record packed ring first dequeue desc index */
>>         uint16_t                shadow_last_used_idx;
>> -       struct vhost_vring_addr ring_addrs;
>>
>> -       struct batch_copy_elem  *batch_copy_elems;
>>         uint16_t                batch_copy_nb_elems;
>> +       struct batch_copy_elem  *batch_copy_elems;
>>         bool                    used_wrap_counter;
>>         bool                    avail_wrap_counter;
>>
>> -       struct log_cache_entry *log_cache;
>> +       /* Physical address of used ring, for logging */
>>         uint16_t log_cache_nb_elem;
> 
> Indent is broken / not consistent, probably because you cut/pasted lines.

Will fix it.

Thanks,
Maxime