diff options
| author | Will Deacon <will@kernel.org> | 2025-07-17 12:01:11 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-28 17:28:25 +0300 |
| commit | c2bdb45f366a90dab68e08a95fb0762ad76a9f68 (patch) | |
| tree | 9fda884d248e5fe616116f57198a589355c70aee /include/linux/virtio_vsock.h | |
| parent | bc9ef9783c6bd10518103c8924088879606fe9f4 (diff) | |
| download | linux-c2bdb45f366a90dab68e08a95fb0762ad76a9f68.tar.xz | |
vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page
[ Upstream commit 03a92f036a04fed2b00d69f5f46f1a486e70dc5c ]
When allocating receive buffers for the vsock virtio RX virtqueue, an
SKB is allocated with a 4140 data payload (the 44-byte packet header +
VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE). Even when factoring in the SKB
overhead, the resulting 8KiB allocation thanks to the rounding in
kmalloc_reserve() is wasteful (~3700 unusable bytes) and results in a
higher-order page allocation on systems with 4KiB pages just for the
sake of a few hundred bytes of packet data.
Limit the vsock virtio RX buffers to 4KiB per SKB, resulting in much
better memory utilisation and removing the need to allocate higher-order
pages entirely.
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>
Message-Id: <20250717090116.11987-5-will@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include/linux/virtio_vsock.h')
| -rw-r--r-- | include/linux/virtio_vsock.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h index fbf30721bac9..5148b035a8f3 100644 --- a/include/linux/virtio_vsock.h +++ b/include/linux/virtio_vsock.h @@ -110,7 +110,12 @@ static inline size_t virtio_vsock_skb_len(struct sk_buff *skb) return (size_t)(skb_end_pointer(skb) - skb->head); } -#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 4) +/* Dimension the RX SKB so that the entire thing fits exactly into + * a single 4KiB page. This avoids wasting memory due to alloc_skb() + * rounding up to the next page order and also means that we + * don't leave higher-order pages sitting around in the RX queue. + */ +#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE SKB_WITH_OVERHEAD(1024 * 4) #define VIRTIO_VSOCK_MAX_BUF_SIZE 0xFFFFFFFFUL #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE (1024 * 64) |