vhost: move dirty logging cache out of virtqueue

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>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Tested-by: Balazs Nemeth <bnemeth@redhat.com>

diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 5a7c0c6..a8032e3 100644 (file)
--- 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_atomic_thread_fence(__ATOMIC_RELEASE);
+               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 +366,7 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue *vq)
        }
        rte_free(vq->batch_copy_elems);
        rte_mempool_free(vq->iotlb_pool);
+       rte_free(vq->log_cache);
        rte_free(vq);
 }
 

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 717f410..3a71dfe 100644 (file)
--- 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 a60bb94..4d9e76e 100644 (file)
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -2022,6 +2022,9 @@ vhost_user_get_vring_base(struct virtio_net **pdev,
        rte_free(vq->batch_copy_elems);
        vq->batch_copy_elems = NULL;
 
+       rte_free(vq->log_cache);
+       vq->log_cache = NULL;
+
        msg->size = sizeof(msg->payload.state);
        msg->fd_num = 0;
 
@@ -2121,6 +2124,7 @@ 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 +2178,23 @@ 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];
+
+               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.