From: Bruce Richardson <bruce.richardson@intel.com>
To: Ivan Boule <ivan.boule@6wind.com>
Cc: Jerin Jacob <jerin.jacob@caviumnetworks.com>,
dev@dpdk.org, pablo.de.lara.guarch@intel.com
Subject: Re: [dpdk-dev] [PATCH] app/testpmd: add packet data prefetch in macswap loop
Date: Tue, 3 May 2016 11:20:21 +0100 [thread overview]
Message-ID: <20160503102021.GB15716@bricha3-MOBL3> (raw)
In-Reply-To: <57287467.7080702@6wind.com>
On Tue, May 03, 2016 at 11:50:31AM +0200, Ivan Boule wrote:
> On 05/03/2016 11:45 AM, Bruce Richardson wrote:
> >On Mon, May 02, 2016 at 05:29:37PM +0530, Jerin Jacob wrote:
> >>prefetch the next packet data address in advance in macswap loop
> >>for performance improvement.
> >>
> >>...
> >> for (i = 0; i < nb_rx; i++) {
> >>+ if (likely(i < nb_rx - 1))
> >>+ rte_prefetch0(rte_pktmbuf_mtod(pkts_burst[i + 1],
> >>+ void *));
> >
> >At least on IA platforms, there is no issue with prefetching beyond the end of
> >the array, since it's only a hint to the cpu. If this is true for other platforms,
> >then I suggest we just drop the conditional and just always prefetch.
>
> This is an interesting point.
> Bruce, are you suggesting that prefetching at an invalid [virtual] address
> won't trigger a CPU exception?
>
Yep. For example, adding "rte_prefetch0(NULL)" at the start of main in testpmd
causes no ill effects when running the app.
/Bruce
next prev parent reply other threads:[~2016-05-03 10:20 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-02 11:59 Jerin Jacob
2016-05-02 17:48 ` De Lara Guarch, Pablo
2016-05-03 12:46 ` Jerin Jacob
2016-05-03 9:45 ` Bruce Richardson
2016-05-03 9:48 ` De Lara Guarch, Pablo
2016-05-03 10:16 ` Bruce Richardson
2016-05-03 9:50 ` Ivan Boule
2016-05-03 10:20 ` Bruce Richardson [this message]
2016-05-10 12:26 ` Ananyev, Konstantin
2016-05-03 14:07 ` [dpdk-dev] [PATCH v2] app/testpmd: add packet data pointer prefetch in the forwarding loop Jerin Jacob
2016-05-03 14:33 ` Thomas Monjalon
2016-06-07 11:19 ` De Lara Guarch, Pablo
2016-06-08 15:57 ` Thomas Monjalon
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