From: "Yang, Zhiyong" <zhiyong.yang@intel.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>,
Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: "Liang, Cunming" <cunming.liang@intel.com>,
"Tan, Jianfeng" <jianfeng.tan@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [RFC PATCH] net/virtio: Align Virtio-net header on cache line in receive path
Date: Wed, 22 Feb 2017 02:49:05 +0000 [thread overview]
Message-ID: <E182254E98A5DA4EB1E657AC7CB9BD2A3EB7257A@BGSMSX101.gar.corp.intel.com> (raw)
In-Reply-To: <20170222013734.GJ18844@yliu-dev.sh.intel.com>
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Yuanhan Liu
> Sent: Wednesday, February 22, 2017 9:38 AM
> To: Maxime Coquelin <maxime.coquelin@redhat.com>
> Cc: Liang, Cunming <cunming.liang@intel.com>; Tan, Jianfeng
> <jianfeng.tan@intel.com>; dev@dpdk.org
> Subject: Re: [dpdk-dev] [RFC PATCH] net/virtio: Align Virtio-net header on
> cache line in receive path
>
> On Tue, Feb 21, 2017 at 06:32:43PM +0100, Maxime Coquelin wrote:
> > This patch aligns the Virtio-net header on a cache-line boundary to
> > optimize cache utilization, as it puts the Virtio-net header (which is
> > always accessed) on the same cache line as the packet header.
> >
> > For example with an application that forwards packets at L2 level, a
> > single cache-line will be accessed with this patch, instead of two
> > before.
>
> I'm assuming you were testing pkt size <= (64 - hdr_size)?
>
> > In case of multi-buffers packets, next segments will be aligned on a
> > cache-line boundary, instead of cache-line boundary minus size of vnet
> > header before.
>
> The another thing is, this patch always makes the pkt data cache unaligned
> for the first packet, which makes Zhihong's optimization on memcpy (for big
> packet) useless.
Why not could we keep pkt data starting always on the cache-line boundary?
In case of multi-buffer, the first remains unchanged, next segments can do as
Maxime said that.
Thanks
Zhiyong
next prev parent reply other threads:[~2017-02-22 2:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-21 17:32 Maxime Coquelin
2017-02-22 1:37 ` Yuanhan Liu
2017-02-22 2:49 ` Yang, Zhiyong [this message]
2017-02-22 9:39 ` Maxime Coquelin
2017-02-22 9:36 ` Maxime Coquelin
2017-02-23 5:49 ` Yuanhan Liu
2017-03-01 7:36 ` Maxime Coquelin
2017-03-06 8:46 ` Yuanhan Liu
2017-03-06 14:11 ` Maxime Coquelin
2017-03-08 6:01 ` Yao, Lei A
2017-03-09 14:38 ` Maxime Coquelin
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