From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>, dev@dpdk.org
Cc: Tan Jianfeng <jianfeng.tan@intel.com>,
Wang Zhihong <zhihong.wang@intel.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
stable@dpdk.org
Subject: Re: [dpdk-stable] [PATCH 2/2] net/virtio: optimize header reset on any layout
Date: Wed, 11 Jan 2017 09:01:21 +0100 [thread overview]
Message-ID: <5df60187-ced5-56d0-9894-3e6783209c3b@redhat.com> (raw)
In-Reply-To: <1484108832-19907-3-git-send-email-yuanhan.liu@linux.intel.com>
On 01/11/2017 05:27 AM, Yuanhan Liu wrote:
> When any layout is used, the header is stored in the head room of mbuf.
> mbuf is allocated and filled by user, means there is no gurateen the
> header is all zero for non TSO case. Therefore, we have to do the reset
> by ourself:
>
> memest(hdr, 0, head_size);
>
> The memset has two impacts on performance:
>
> - memset could not be inlined, which is a bit costly.
> - more importantly, it touches the mbuf, which could introduce severe
> cache issues as described by former patch.
>
> Similiary, we could do the same trick: reset just when necessary, when
> the corresponding field is already 0, which is likely true for a simple
> l2 forward case. It could boost the performance up to 20+% in micro
> benchmarking.
>
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: stable@dpdk.org
> Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
> ---
> drivers/net/virtio/virtio_rxtx.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 8ec2f1a..5ca3a88 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -292,8 +292,14 @@
> hdr = (struct virtio_net_hdr *)
> rte_pktmbuf_prepend(cookie, head_size);
> /* if offload disabled, it is not zeroed below, do it now */
> - if (offload == 0)
> - memset(hdr, 0, head_size);
> + if (offload == 0) {
> + ASSIGN_UNLESS_EQUAL(hdr->csum_start, 0);
> + ASSIGN_UNLESS_EQUAL(hdr->csum_offset, 0);
> + ASSIGN_UNLESS_EQUAL(hdr->flags, 0);
> + ASSIGN_UNLESS_EQUAL(hdr->gso_type, 0);
> + ASSIGN_UNLESS_EQUAL(hdr->gso_size, 0);
> + ASSIGN_UNLESS_EQUAL(hdr->hdr_len, 0);
> + }
> } else if (use_indirect) {
> /* setup tx ring slot to point to indirect
> * descriptor list stored in reserved region.
>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Thanks!
Maxime
prev parent reply other threads:[~2017-01-11 8:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1484108832-19907-1-git-send-email-yuanhan.liu@linux.intel.com>
2017-01-11 4:27 ` [dpdk-stable] [PATCH 1/2] net/virtio: fix performance regression due to TSO enabling Yuanhan Liu
2017-01-11 7:59 ` Maxime Coquelin
2017-01-11 8:08 ` Yuanhan Liu
2017-01-11 8:22 ` Olivier MATZ
2017-01-11 4:27 ` [dpdk-stable] [PATCH 2/2] net/virtio: optimize header reset on any layout Yuanhan Liu
2017-01-11 8:01 ` Maxime Coquelin [this message]
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