On Mon, Feb 25, 2019 at 11:13:11AM +0100, Claudio Jeker wrote:
> On Mon, Feb 25, 2019 at 08:08:32PM +1000, David Gwynne wrote:
> > On Mon, Feb 25, 2019 at 08:44:35AM +0100, Claudio Jeker wrote:
> > > On Mon, Feb 25, 2019 at 10:49:16AM +1000, David Gwynne wrote:
> > > > the mcl2k2 pool, aka the intel mbuf cluster pool, gets set up to
> > > > allocate
> > > > at least 2048 + 2 bytes, which gets rounded up by 64 bytes to 2112
> > > > bytes. this diff makes ix move the reception of packets to the end of
> > > > the 2112 byte allocation so there's space left at the front of the mbuf.
> > > >
> > > > this in turn makes it more likely that an m_prepend at another point in
> > > > the system will work without an extra mbuf allocation. eg, if you're
> > > > bridging or routing between vlans and vlans on svlans somewhere else,
> > > > this will be a bit faster with this diff.
> > > >
> > > > thoughts? ok?
> > >
> > > I think using m_align() here may be benefitial. Since it does exactly
> > > that. Apart from that I have to agree, shifting the packet back makes a
> > > lot of sense.
> >
> > Like this?
>
> OK claudio@
Actually no, my bad. m_align() will align the buffer to a long word
boundary and that's not what we want. But your first diff is also not
quite right since m_len is modified by m_align and so the length is
getting < 2048. (which may not matter here but better be 100% correct).
Setting mp->m_len = mp->m_pkthdr.len = mp->m_ext.ext_size should do the
trick.
mp->m_len = mp->m_pkthdr.len = mp->m_ext.ext_size;
m_adj(mp, mp->m_ext.ext_size - sc->rx_mbuf_sz;
At least this should do what we want.
> > Index: if_ix.c
> > ===================================================================
> > RCS file: /cvs/src/sys/dev/pci/if_ix.c,v
> > retrieving revision 1.153
> > diff -u -p -r1.153 if_ix.c
> > --- if_ix.c 21 Feb 2019 03:16:47 -0000 1.153
> > +++ if_ix.c 25 Feb 2019 10:06:59 -0000
> > @@ -2389,8 +2395,8 @@ ixgbe_get_buf(struct rx_ring *rxr, int i
> > if (!mp)
> > return (ENOBUFS);
> >
> > + m_align(mp, sc->rx_mbuf_sz);
> > mp->m_len = mp->m_pkthdr.len = sc->rx_mbuf_sz;
> > - m_adj(mp, ETHER_ALIGN);
> >
> > error = bus_dmamap_load_mbuf(rxr->rxdma.dma_tag, rxbuf->map,
> > mp, BUS_DMA_NOWAIT);
> >
>
> --
> :wq Claudio
>
--
:wq Claudio
