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From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
To: "Morten Brørup" <mb@smartsharesystems.com>,
	"Mattias Rönnblom" <hofors@lysator.liu.se>,
	"Stephen Hemminger" <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	Bruce Richardson <bruce.richardson@intel.com>,
	Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>,
	Jan Viktorin <viktorin@rehivetech.com>,
	Ruifeng Wang <Ruifeng.Wang@arm.com>,
	David Christensen <drc@linux.vnet.ibm.com>,
	Stanislaw Kardach <kda@semihalf.com>, nd <nd@arm.com>,
	nd <nd@arm.com>
Subject: RE: [RFC v2] non-temporal memcpy
Date: Wed, 10 Aug 2022 21:20:32 +0000	[thread overview]
Message-ID: <DBAPR08MB581416981BE41DBB593DD85998659@DBAPR08MB5814.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35D87253@smartserver.smartshare.dk>

<snip>

> 
> > From: Mattias Rönnblom [mailto:hofors@lysator.liu.se]
> > Sent: Wednesday, 10 August 2022 13.56
> >
> > On 2022-08-09 17:26, Stephen Hemminger wrote:
> 
> [...]
> 
> >
> > Alignment seems like a non-issue to me. A NT-store memcpy() can be
> > made free of alignment requirements, incurring only a very slight cost
> > for the always-aligned case (who has their data always 16-byte aligned
> > anyways?).
> >
> > The memory barrier required on x86 seems like a bigger issue.
> >
> > > Maybe rte_non_cache_copy()?
> > >
> >
> > rte_memcpy_nt_weakly_ordered(), or rte_memcpy_nt_weak(). And a
> > rte_memcpy_nt() with the sfence is place, which the user hopefully
> > will find first? I don't know. I would prefer not having the weak
> > variant at all.
I think providing weakly ordered version is required to offset the cost of the barriers. One might be able to copy multiple packets and then issue a barrier.

> >
> > Accepting weak memory ordering (i.e., no sfence) could also be one of
> > the flags, assuming rte_memcpy_nt() would have a flags parameter.
> > Default is safe (=memcpy() semantics), but potentially slower.
> 
> Excellent idea!
> 
> >
> > > Want to avoid the naive user just doing s/memcpy/rte_memcpy_nt/ and
> > expect
> > > everything to work.


  reply	other threads:[~2022-08-10 21:20 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-19 15:26 Morten Brørup
2022-07-19 18:00 ` David Christensen
2022-07-19 18:41   ` Morten Brørup
2022-07-19 18:51     ` Stanisław Kardach
2022-07-19 22:15       ` Morten Brørup
2022-07-21 23:19 ` Konstantin Ananyev
2022-07-22 10:44   ` Morten Brørup
2022-07-24 13:35     ` Konstantin Ananyev
2022-07-24 22:18       ` Morten Brørup
2022-07-29 10:00         ` Konstantin Ananyev
2022-07-29 10:46           ` Morten Brørup
2022-07-29 11:50             ` Konstantin Ananyev
2022-07-29 17:17               ` Morten Brørup
2022-07-29 22:00                 ` Konstantin Ananyev
2022-07-30  9:51                   ` Morten Brørup
2022-08-02  9:05                     ` Konstantin Ananyev
2022-07-29 12:13             ` Konstantin Ananyev
2022-07-29 16:05               ` Stephen Hemminger
2022-07-29 17:29                 ` Morten Brørup
2022-08-07 20:40                 ` Mattias Rönnblom
2022-08-09  9:24                   ` Morten Brørup
2022-08-09 11:53                     ` Mattias Rönnblom
2022-10-09 16:16                       ` Morten Brørup
2022-07-29 18:13               ` Morten Brørup
2022-07-29 19:49                 ` Konstantin Ananyev
2022-07-29 20:26                   ` Morten Brørup
2022-07-29 21:34                     ` Konstantin Ananyev
2022-08-07 20:20                     ` Mattias Rönnblom
2022-08-09  9:34                       ` Morten Brørup
2022-08-09 11:56                         ` Mattias Rönnblom
2022-08-10 21:05                     ` Honnappa Nagarahalli
2022-08-11 11:50                       ` Mattias Rönnblom
2022-08-11 16:26                         ` Honnappa Nagarahalli
2022-07-25  1:17       ` Honnappa Nagarahalli
2022-07-27 10:26         ` Morten Brørup
2022-07-27 17:37           ` Honnappa Nagarahalli
2022-07-27 18:49             ` Morten Brørup
2022-07-27 19:12               ` Stephen Hemminger
2022-07-28  9:00                 ` Morten Brørup
2022-07-27 19:52               ` Honnappa Nagarahalli
2022-07-27 22:02                 ` Stanisław Kardach
2022-07-28 10:51                   ` Morten Brørup
2022-07-29  9:21                     ` Konstantin Ananyev
2022-08-07 20:25 ` Mattias Rönnblom
2022-08-09  9:46   ` Morten Brørup
2022-08-09 12:05     ` Mattias Rönnblom
2022-08-09 15:00       ` Morten Brørup
2022-08-10 11:47         ` Mattias Rönnblom
2022-08-09 15:26     ` Stephen Hemminger
2022-08-09 17:24       ` Morten Brørup
2022-08-10 11:59         ` Mattias Rönnblom
2022-08-10 12:12           ` Morten Brørup
2022-08-10 11:55       ` Mattias Rönnblom
2022-08-10 12:18         ` Morten Brørup
2022-08-10 21:20           ` Honnappa Nagarahalli [this message]
2022-08-11 11:53             ` Mattias Rönnblom
2022-08-11 22:24               ` Honnappa Nagarahalli

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