From: "Morten Brørup" <mb@smartsharesystems.com>
To: "Honnappa Nagarahalli" <Honnappa.Nagarahalli@arm.com>,
"Olivier Matz" <olivier.matz@6wind.com>
Cc: <dev@dpdk.org>
Subject: Re: [dpdk-dev] rte_mbuf library likely()/unlikely()
Date: Mon, 23 Jul 2018 21:09:37 +0200 [thread overview]
Message-ID: <98CBD80474FA8B44BF855DF32C47DC35B421F1@smartserver.smartshare.dk> (raw)
In-Reply-To: <HE1PR0801MB1930747F372E5B543B4F273098560@HE1PR0801MB1930.eurprd08.prod.outlook.com>
I haven't performance tested, but they are compiler branch prediction hints pointing out the most likely execution path, so I expect them to have a positive effect.
E.g. the first comparison in __rte_pktmbuf_read() is very unlikely to be true - it would mean that the application is trying to read data beyond the packet.
Please also refer to:
https://cellperformance.beyond3d.com/articles/2006/04/branch-patterns-using-gcc.html
> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Honnappa Nagarahalli
> Sent: Monday, July 23, 2018 7:52 PM
> To: Morten Brørup; Olivier Matz
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] rte_mbuf library likely()/unlikely()
>
> Do you see any performance improvements with these changes?
>
> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Morten Brørup
> Sent: Monday, July 23, 2018 8:54 AM
> To: Olivier Matz <olivier.matz@6wind.com>
> Cc: dev@dpdk.org
> Subject: [dpdk-dev] rte_mbuf library likely()/unlikely()
>
> Hi Olivier,
>
>
>
> I noticed that __rte_pktmbuf_read() could do with an unlikely(), so I went
> through the entire library. Here are my suggested modifications.
>
next prev parent reply other threads:[~2018-07-23 19:09 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-23 13:53 Morten Brørup
2018-07-23 17:37 ` Stephen Hemminger
2018-07-23 18:59 ` Morten Brørup
2018-07-23 19:45 ` Stephen Hemminger
2018-07-23 17:51 ` Honnappa Nagarahalli
2018-07-23 19:09 ` Morten Brørup [this message]
2018-07-23 22:40 ` Wiles, Keith
2018-07-24 7:29 ` Olivier Matz
2018-07-24 8:13 ` Morten Brørup
2018-07-24 11:31 ` Van Haaren, Harry
2018-07-24 13:02 ` Wiles, Keith
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