Messages in this thread | | | Date | Thu, 03 Apr 2014 14:23:38 -0400 (EDT) | Subject | Re: [PATCH net-next v3 2/2] xen-netback: Grant copy the header instead of map and memcpy | From | David Miller <> |
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From: Zoltan Kiss <zoltan.kiss@citrix.com> Date: Wed, 2 Apr 2014 18:04:58 +0100
> An old inefficiency of the TX path that we are grant mapping the first slot, > and then copy the header part to the linear area. Instead, doing a grant copy > for that header straight on is more reasonable. Especially because there are > ongoing efforts to make Xen avoiding TLB flush after unmap when the page were > not touched in Dom0. In the original way the memcpy ruined that. > The key changes: > - the vif has a tx_copy_ops array again > - xenvif_tx_build_gops sets up the grant copy operations > - we don't have to figure out whether the header and first frag are on the same > grant mapped page or not > Note, we only grant copy PKT_PROT_LEN bytes from the first slot, the rest (if > any) will be on the first frag, which is grant mapped. If the first slot is > smaller than PKT_PROT_LEN, then we grant copy that, and later __pskb_pull_tail > will pull more from the frags (if any) > > Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Applied.
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