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From: David Marchand <david.marchand@redhat.com>
To: Bruce Richardson <bruce.richardson@intel.com>
Cc: Omkar Maslekar <omkar.maslekar@intel.com>, dev <dev@dpdk.org>,
	 "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
	Ciara Loftus <ciara.loftus@intel.com>,
	 David Christensen <drc@linux.vnet.ibm.com>,
	Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
	 Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	 "Ruifeng Wang (Arm Technology China)" <ruifeng.wang@arm.com>,
	Jan Viktorin <viktorin@rehivetech.com>,
	 Thomas Monjalon <thomas@monjalon.net>
Subject: Re: [dpdk-dev] [PATCH v5] eal: add cache-line demote support
Date: Mon, 12 Oct 2020 11:41:19 +0200
Message-ID: <CAJFAV8x3B2GEzeVZx6naNVs21asmCoui=s6J3Tx5F__rrShOWA@mail.gmail.com> (raw)
In-Reply-To: <20201008090243.GA1106@bricha3-MOBL.ger.corp.intel.com>

On Thu, Oct 8, 2020 at 11:02 AM Bruce Richardson
<bruce.richardson@intel.com> wrote:
>
> On Thu, Oct 08, 2020 at 09:09:52AM +0200, David Marchand wrote:
> > On Thu, Oct 1, 2020 at 2:30 AM Omkar Maslekar <omkar.maslekar@intel.com> wrote:
> > >
> > > rte_cldemote is similar to a prefetch hint - in reverse. cldemote(addr)
> > > enables software to hint to hardware that line is likely to be shared.
> > > Useful in core-to-core communications where cache-line is likely to be
> > > shared. ARM and PPC implementation is provided with NOP and can be added
> > > if any equivalent instructions could be used for implementation on those
> > > architectures.
> > >
> > > Signed-off-by: Omkar Maslekar <omkar.maslekar@intel.com>
> > > Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> >
> > I find this "rte_cldemote" name too close to the Intel instruction,
> > but I can see no complaint from other arch maintainers, so I guess
> > everyone is happy with it.
>
> It is very close, alright - though the name too does fairly well convey the
> likely actual done by the instruction.. Is there a suggestion for a better,
> more generic name.

I don't have a better suggestion.


The prefetch API has some hints on the level of cache to put data in.
For this new API, we have no indication, would it make sense?


Is this available on all Intel CPUs supported with DPDK?
No cpuflag check needed?


>
> > In any case, this is a new API, so it should be marked experimental.
> >
> Agreed.
>
> > As for unit tests, not sure there is much to do, maybe rename
> > test_prefetch.c and call this new API too, wdyt?
> >
> I'm not sure how much value this would provide, but it can be done.

As much as the existing test, checking we can call this API.
If you think it is not worth it, we can drop the prefetch ut code.


-- 
David Marchand


  reply	other threads:[~2020-10-12  9:41 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-10  1:16 [dpdk-dev] [PATCH] EAL: An addition of cache line demote (CLDEMOTE) in rte_prefetch.h Omkar Maslekar
2020-09-10  1:16 ` Omkar Maslekar
2020-09-10  8:55   ` Bruce Richardson
2020-09-10 23:30     ` Maslekar, Omkar
2020-09-10 22:04   ` David Christensen
2020-09-11 16:51 ` [dpdk-dev] [PATCH v2] " Omkar Maslekar
2020-09-11 16:51   ` Omkar Maslekar
2020-09-11 21:22 ` [dpdk-dev] [PATCH v3] " Omkar Maslekar
2020-09-11 21:22   ` Omkar Maslekar
2020-09-22  1:59 ` [dpdk-dev] [PATCH v4] eal: add cache-line demote support Omkar Maslekar
2020-09-22  1:59   ` Omkar Maslekar
2020-09-22  8:28     ` Bruce Richardson
2020-09-22 21:53       ` Maslekar, Omkar
2020-10-01  0:28 ` [dpdk-dev] [PATCH v5] " Omkar Maslekar
2020-10-01  0:28   ` Omkar Maslekar
2020-10-08  7:09     ` David Marchand
2020-10-08  9:02       ` Bruce Richardson
2020-10-12  9:41         ` David Marchand [this message]
2020-10-08 13:12     ` Jerin Jacob
2020-10-12 10:19 ` [dpdk-dev] [PATCH v6] " Omkar Maslekar
2020-10-12 10:19   ` Omkar Maslekar
2020-10-12 19:31     ` David Christensen
2020-10-13  2:59     ` Ruifeng Wang
2020-10-13 16:20       ` Bruce Richardson
2020-10-14  1:55         ` Ruifeng Wang
2020-10-14  7:14         ` David Marchand
2020-10-14  7:51           ` Ruifeng Wang
2020-10-13  9:43 ` [dpdk-dev] [PATCH v7] " Omkar Maslekar
2020-10-13  9:43   ` Omkar Maslekar
2020-10-14  7:24     ` Ruifeng Wang
2020-10-15  8:01     ` David Marchand
2020-10-15 14:41       ` Maslekar, Omkar
2020-10-15 20:32         ` David Marchand
2020-10-15 15:18 ` [dpdk-dev] [PATCH v8] " Omkar Maslekar
2020-10-15 15:18   ` Omkar Maslekar
2020-10-15 23:20 ` [dpdk-dev] [PATCH v9] " Omkar Maslekar
2020-10-15 23:20   ` Omkar Maslekar
2020-10-16 12:14     ` David Marchand

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