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From: Thomas Monjalon <thomas@monjalon.net>
To: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"Liu, Yong" <yong.liu@intel.com>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	"dev@dpdk.org" <dev@dpdk.org>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	"Yigit, Ferruh" <ferruh.yigit@intel.com>,
	"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>,
	David Christensen <drc@linux.vnet.ibm.com>,
	Ruifeng Wang <Ruifeng.Wang@arm.com>, nd <nd@arm.com>
Subject: Re: [dpdk-dev] [PATCH v2] config: enable packet data prefetch
Date: Thu, 15 Oct 2020 11:21:07 +0200
Message-ID: <3677226.MZCibFMyqQ@thomas> (raw)
In-Reply-To: <20b8cb3f50b241bfb4e5381b2090a150@intel.com>

15/10/2020 10:23, Liu, Yong:
> From: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
> > > > 23/09/2020 03:51, Marvin Liu:
> > > > > Data prefetch instruction can preload data into cpu’s hierarchical
> > > > > cache before data access. Virtualized data paths like virtio
> > > > > utilized this feature for acceleration. Since most modern cpus have
> > > > > support prefetch function, we can enable packet data prefetch as
> > default.
> > > > >
> > > > > Signed-off-by: Marvin Liu <yong.liu@intel.com>
> > > > > ---
> > > > > +#define RTE_PMD_PACKET_PREFETCH 1
> > > >
> > > > We could also remove the related #ifdefs.
> > > >
> > > > What can be the drawback of always enable those prefetches?
> > > >
> > >
> > > Hi Thomas,
> > > I think the potential drawback is that current prefetch location cannot
> > > guarantee the best performance across different platforms.
> > Then, does it make sense to enable this by default?
> > 
> 
> Now most of prefetch actions are placed after pointer of data is valid.  I think this methodology can benefit all platforms.
> It's hard to say that it’s the best choice for all. But no more better solution in my mind. 
> At least, we need to allow user to enable packet data prefetch.

In my opinion, it can be tested and measured.

> > > Each developer has tuned the performance by adding prefetch instruction
> > > and verified the result on himself platform.
> > > So prefetch location is based on certain platform, also it will be hard for
> > > developer to compare the results across platforms.

If it shows benefit on an architecture, then it should be enabled
with #ifdef RTE_ARCH_XX

I am for removing the option RTE_PMD_PACKET_PREFETCH.




  reply	other threads:[~2020-10-15  9:21 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-22  8:21 [dpdk-dev] [PATCH] build: " Marvin Liu
2020-09-22 14:11 ` Stephen Hemminger
2020-09-23  2:00   ` Liu, Yong
2020-09-23  1:51 ` [dpdk-dev] [PATCH v2] config: " Marvin Liu
2020-10-14 22:02   ` Thomas Monjalon
2020-10-15  1:21     ` Liu, Yong
2020-10-15  4:09       ` Honnappa Nagarahalli
2020-10-15  8:23         ` Liu, Yong
2020-10-15  9:21           ` Thomas Monjalon [this message]
2020-10-15 14:38             ` Honnappa Nagarahalli
2020-11-03  1:57   ` [dpdk-dev] [PATCH v3] drivers/net: enable packet data prefetch on x86 Marvin Liu

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