Messages in this thread | | | Subject | Re: [PATCH net-next v3 2/2] xen-netback: Grant copy the header instead of map and memcpy | From | Ian Campbell <> | Date | Thu, 3 Apr 2014 10:11:14 +0100 |
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On Thu, 2014-04-03 at 09:07 +0100, Paul Durrant wrote: > > -----Original Message----- > > From: Zoltan Kiss > > Sent: 02 April 2014 18:05 > > To: Ian Campbell; Wei Liu; xen-devel@lists.xenproject.org > > Cc: Paul Durrant; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; > > Jonathan Davies; Zoltan Kiss > > Subject: [PATCH net-next v3 2/2] xen-netback: Grant copy the header > > instead of map and memcpy > > > > 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> > > Looks good to me. > > Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Me too:
Acked-by: Ian Campbell <ian.campbell@citrix.com>
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