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hw/net/virtio-net: skip automatic zero-init of large arrays

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The 'virtio_net_receive_rcu' method has three arrays with
VIRTQUEUE_MAX_SIZE elements, which are apprixmately 32k in
size used for copying data between guest and host. Skip the
automatic zero-init of these arrays to eliminate the
performance overhead in the I/O hot path.

The three arrays will be selectively initialized as required
when processing network buffers.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20250610123709.835102-22-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2025-06-10 13:36:59 +01:00 • committed by Stefan Hajnoczi
parent e1afd5ee6e
commit 21cf31c51a
1 changed files with 3 additions and 3 deletions
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6
hw/net/virtio-net.c
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@ -1911,9 +1911,9 @@ static ssize_t virtio_net_receive_rcu(NetClientState *nc, const uint8_t *buf,
VirtIONet *n = qemu_get_nic_opaque(nc);
VirtIONetQueue *q;
VirtIODevice *vdev = VIRTIO_DEVICE(n);
VirtQueueElement *elems[VIRTQUEUE_MAX_SIZE];
size_t lens[VIRTQUEUE_MAX_SIZE];
struct iovec mhdr_sg[VIRTQUEUE_MAX_SIZE];
QEMU_UNINITIALIZED VirtQueueElement *elems[VIRTQUEUE_MAX_SIZE];
QEMU_UNINITIALIZED size_t lens[VIRTQUEUE_MAX_SIZE];
QEMU_UNINITIALIZED struct iovec mhdr_sg[VIRTQUEUE_MAX_SIZE];
struct virtio_net_hdr_v1_hash extra_hdr;
unsigned mhdr_cnt = 0;
size_t offset, i, guest_offset, j;