From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc: Shay Agroskin <shayagr@amazon.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
bpf@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net,
kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net,
toke@redhat.com, freysteinn.alfredsson@kau.se,
john.fastabend@gmail.com, jasowang@redhat.com, mst@redhat.com,
thomas.petazzoni@bootlin.com, mw@semihalf.com,
linux@armlinux.org.uk, ilias.apalodimas@linaro.org,
netanel@amazon.com, akiyano@amazon.com,
michael.chan@broadcom.com, madalin.bucur@nxp.com,
ioana.ciornei@nxp.com, jesse.brandeburg@intel.com,
anthony.l.nguyen@intel.com, saeedm@nvidia.com,
grygorii.strashko@ti.com, ecree.xilinx@gmail.com,
brouer@redhat.com
Subject: Re: [PATCH v2 bpf-next] bpf: devmap: move drop error path to devmap for XDP_REDIRECT
Date: Mon, 1 Mar 2021 08:48:47 +0100 [thread overview]
Message-ID: <20210301084847.5117a404@carbon> (raw)
In-Reply-To: <YDwYzYVIDQABINyy@lore-laptop-rh>
On Sun, 28 Feb 2021 23:27:25 +0100
Lorenzo Bianconi <lorenzo.bianconi@redhat.com> wrote:
> > > drops = bq->count - sent;
> > > -out:
> > > - bq->count = 0;
> > > + if (unlikely(drops > 0)) {
> > > + /* If not all frames have been transmitted, it is our
> > > + * responsibility to free them
> > > + */
> > > + for (i = sent; i < bq->count; i++)
> > > + xdp_return_frame_rx_napi(bq->q[i]);
> > > + }
> >
> > Wouldn't the logic above be the same even w/o the 'if' condition ?
>
> it is just an optimization to avoid the for loop instruction if sent = bq->count
True, and I like this optimization.
It will affect how the code layout is (and thereby I-cache usage).
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2021-03-01 7:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-27 11:04 [PATCH v2 bpf-next] bpf: devmap: move drop error path to devmap for XDP_REDIRECT Lorenzo Bianconi
2021-02-28 12:15 ` Shay Agroskin
2021-02-28 22:27 ` Lorenzo Bianconi
2021-03-01 7:48 ` Jesper Dangaard Brouer [this message]
2021-03-01 11:23 ` Shay Agroskin
2021-03-01 20:18 ` Jesper Dangaard Brouer
2021-03-02 15:28 ` Lorenzo Bianconi
2021-03-03 11:29 ` Shay Agroskin
2021-03-01 11:59 ` Ioana Ciornei
2021-03-01 12:26 ` Ilias Apalodimas
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