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authorPaolo Bonzini <pbonzini@redhat.com>2016-02-04 16:26:51 +0200
committerMichael S. Tsirkin <mst@redhat.com>2016-02-06 20:39:07 +0200
commit51b19ebe4320f3dcd93cea71235c1219318ddfd2 (patch)
treea242566284e7efb7a45e151481b0433a3ffe39b5 /hw/virtio/virtio-rng.c
parent6aa46d8ff1ee7e9ca0c4a54d75c74108bee22124 (diff)
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virtio: move allocation to virtqueue_pop/vring_pop
The return code of virtqueue_pop/vring_pop is unused except to check for errors or 0. We can thus easily move allocation inside the functions and just return a pointer to the VirtQueueElement. The advantage is that we will be able to allocate only the space that is needed for the actual size of the s/g list instead of the full VIRTQUEUE_MAX_SIZE items. Currently VirtQueueElement takes about 48K of memory, and this kind of allocation puts a lot of stress on malloc. By cutting the size by two or three orders of magnitude, malloc can use much more efficient algorithms. The patch is pretty large, but changes to each device are testable more or less independently. Splitting it would mostly add churn. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Diffstat (limited to 'hw/virtio/virtio-rng.c')
-rw-r--r--hw/virtio/virtio-rng.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c
index a80fb89..17da2f8 100644
--- a/hw/virtio/virtio-rng.c
+++ b/hw/virtio/virtio-rng.c
@@ -44,7 +44,7 @@ static void chr_read(void *opaque, const void *buf, size_t size)
{
VirtIORNG *vrng = opaque;
VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
- VirtQueueElement elem;
+ VirtQueueElement *elem;
size_t len;
int offset;
@@ -56,15 +56,17 @@ static void chr_read(void *opaque, const void *buf, size_t size)
offset = 0;
while (offset < size) {
- if (!virtqueue_pop(vrng->vq, &elem)) {
+ elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
+ if (!elem) {
break;
}
- len = iov_from_buf(elem.in_sg, elem.in_num,
+ len = iov_from_buf(elem->in_sg, elem->in_num,
0, buf + offset, size - offset);
offset += len;
- virtqueue_push(vrng->vq, &elem, len);
+ virtqueue_push(vrng->vq, elem, len);
trace_virtio_rng_pushed(vrng, len);
+ g_free(elem);
}
virtio_notify(vdev, vrng->vq);
}