> -----Original Message----- > From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Yuanhan Liu > Sent: Wednesday, February 22, 2017 9:38 AM > To: Maxime Coquelin <maxime.coque...@redhat.com> > Cc: Liang, Cunming <cunming.li...@intel.com>; Tan, Jianfeng > <jianfeng....@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
