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From: "Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)" <jgrajcia@cisco.com>
To: Phil Yang <Phil.Yang@arm.com>,
	Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Cc: Ruifeng Wang <Ruifeng.Wang@arm.com>, nd <nd@arm.com>,
	nd <nd@arm.com>, nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH] net/memif: relax barrier for zero copy path
Date: Mon, 21 Sep 2020 12:21:11 +0000	[thread overview]
Message-ID: <BYAPR11MB35742B06BE3699B4009B5D5DDF3A0@BYAPR11MB3574.namprd11.prod.outlook.com> (raw)
In-Reply-To: <DB7PR08MB386541992259838459E09C0CE93A0@DB7PR08MB3865.eurprd08.prod.outlook.com>

> > > >
> > > > Using 'rte_mb' to synchronize the shared ring head/tail between
> > > > producer and consumer will stall the pipeline and damage
> > > > performance on the weak memory model platforms, such like aarch64.
> > > >
> > > > Relax the expensive barrier with c11 atomic with explicit memory
> > > > ordering can improve 3.6% performance on throughput.
> >
> > My question here is: `rte_mb` is supposed to make sure that head/tail
> > pointer are not updated before the packets are written into shared
> memory.
> > Does the atomic ensures that the packets are written into shared
> > memory before head/tail pointers are updated?
> 
> Yes, it does.
> The atomic store-release acts as a one-way barrier here to make sure all the
> memory accesses before the store-release are observed before it.

Ok then, since the sync is there and the rest seems fine to me.

Thanks,
Jakub

Reviewed-by: Jakub Grajciar <jgrajcia@cisco.com>

  reply	other threads:[~2020-09-21 12:21 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-11  5:38 Phil Yang
2020-09-18 11:58 ` Ferruh Yigit
2020-09-18 22:49 ` Honnappa Nagarahalli
2020-09-21  9:03   ` Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)
2020-09-21 10:22     ` Phil Yang
2020-09-21 12:21       ` Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco) [this message]
2020-09-21 13:27         ` Ferruh Yigit
2020-09-21 19:28     ` Honnappa Nagarahalli

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