[PATCH 6/6] virtio_net: reduce alignment for buffers
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2017-03-29 20:50:25
Also in:
lkml, virtualization
Subsystem:
networking drivers, the rest, virtio net driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, "Michael S. Tsirkin", Jason Wang
We don't need to align length to any particular value anymore. Aligning to L1 cache size probably sill makes sense to reduce false sharing. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- drivers/net/virtio_net.c | 13 +------------ 1 file changed, 1 insertion(+), 12 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 94f94f3..824dd95 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c@@ -53,17 +53,6 @@ module_param(gso, bool, 0444); */ DECLARE_EWMA(pkt_len, 0, 64) -/* With mergeable buffers we align buffer address and use the low bits to - * encode its true size. Buffer size is up to 1 page so we need to align to - * square root of page size to ensure we reserve enough bits to encode the true - * size. - */ -#define MERGEABLE_BUFFER_MIN_ALIGN_SHIFT ((PAGE_SHIFT + 1) / 2) - -/* Minimum alignment for mergeable packet buffers. */ -#define MERGEABLE_BUFFER_ALIGN max(L1_CACHE_BYTES, \ - 1 << MERGEABLE_BUFFER_MIN_ALIGN_SHIFT) - #define VIRTNET_DRIVER_VERSION "1.0.0" struct virtnet_stats {
@@ -849,7 +838,7 @@ static unsigned int get_mergeable_buf_len(struct ewma_pkt_len *avg_pkt_len) len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len), GOOD_PACKET_LEN, PAGE_SIZE - hdr_len); - return ALIGN(len, MERGEABLE_BUFFER_ALIGN); + return ALIGN(len, L1_CACHE_BYTES); } static int add_recvbuf_mergeable(struct virtnet_info *vi,
--
MST