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Date: Wed, 29 Mar 2017 23:48:56 +0300 From: "Michael S. Tsirkin" <mst@...hat.com> To: linux-kernel@...r.kernel.org Cc: John Fastabend <john.fastabend@...il.com>, Jason Wang <jasowang@...hat.com>, virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org Subject: [PATCH 6/6] virtio_net: reduce alignment for buffers 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@...hat.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
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