From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
To: Kurt Kanzenbach <kurt@linutronix.de>
Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>,
Tony Nguyen <anthony.l.nguyen@intel.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Sven Auhagen <sven.auhagen@voleatech.de>,
intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
bpf@vger.kernel.org,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Richard Cochran <richardcochran@gmail.com>,
Alexander Duyck <alexander.duyck@gmail.com>
Subject: Re: [PATCH net v3] igb: Fix XDP with PTP enabled
Date: Fri, 23 Apr 2021 13:51:50 +0200 [thread overview]
Message-ID: <20210423115150.GB64904@ranger.igk.intel.com> (raw)
In-Reply-To: <878s59qz1b.fsf@kurt>
On Fri, Apr 23, 2021 at 08:45:52AM +0200, Kurt Kanzenbach wrote:
> On Thu Apr 22 2021, Maciej Fijalkowski wrote:
> > On Thu, Apr 22, 2021 at 07:26:17AM +0200, Kurt Kanzenbach wrote:
> >> + /* pull rx packet timestamp if available and valid */
> >> + if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
> >> + timestamp = igb_ptp_rx_pktstamp(rx_ring->q_vector,
> >> + pktbuf);
> >> +
> >> + if (timestamp) {
> >> + pkt_offset += IGB_TS_HDR_LEN;
> >> + size -= IGB_TS_HDR_LEN;
> >> + }
> >> + }
> >
> > Small nit: since this is a hot path, maybe we could omit the additional
> > branch that you're introducing above and make igb_ptp_rx_pktstamp() to
> > return either 0 for error cases and IGB_TS_HDR_LEN if timestamp was fine?
> > timestamp itself would be passed as an arg.
> >
> > So:
> > if (igb_test_staterr(rx_desc, E1000_RXDADV_STAT_TSIP)) {
> > ts_offset = igb_ptp_rx_pktstamp(rx_ring->q_vector,
> > pktbuf, ×tamp);
> > pkt_offset += ts_offset;
> > size -= ts_offset;
> > }
> >
> > Thoughts? I feel like if we see that desc has timestamp enabled then let's
> > optimize it for successful case.
>
> Yes, this should work as well. Actually I didn't like the if statement
> either. Only one comment: It's not an offset but rather the timestamp
> header length. I'd call it 'ts_len'.
Right, sorry.
>
> >
> >>
> >> /* retrieve a buffer from the ring */
> >> if (!skb) {
> >> - unsigned int offset = igb_rx_offset(rx_ring);
> >> - unsigned char *hard_start;
> >> + unsigned char *hard_start = pktbuf - igb_rx_offset(rx_ring);
> >> + unsigned int offset = pkt_offset + igb_rx_offset(rx_ring);
> >
> > Probably we could do something similar in flavour of:
> > https://lore.kernel.org/bpf/20210118151318.12324-10-maciej.fijalkowski@intel.com/
> >
> > which broke XDP_REDIRECT and got fixed in:
> > https://lore.kernel.org/bpf/20210303153928.11764-2-maciej.fijalkowski@intel.com/
> >
> > You get the idea.
>
> Yes, I do. However, I think such a change doesn't belong in this patch,
> which is a bugfix for XDP. It looks like an optimization. Should I split
> it into two patches and rather target net-next instead of net?
This was just a heads up from my side as it caught my eye. For sure it's
out of the scope of that patch, but would be good to have a follow up on
that.
>
> Thanks for your review.
>
> Thanks,
> Kurt
prev parent reply other threads:[~2021-04-23 12:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-22 5:26 [PATCH net v3] igb: Fix XDP with PTP enabled Kurt Kanzenbach
2021-04-22 10:11 ` Maciej Fijalkowski
2021-04-23 6:45 ` Kurt Kanzenbach
2021-04-23 11:51 ` Maciej Fijalkowski [this message]
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