netdev - RE: [RFC PATCH 00/30] Kernel NET policy

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Date:	Mon, 18 Jul 2016 17:58:39 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Tom Herbert <tom@...bertland.com>
CC:	Florian Westphal <fw@...len.de>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	"gorcunov@...nvz.org" <gorcunov@...nvz.org>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"aduyck@...antis.com" <aduyck@...antis.com>,
	"ben@...adent.org.uk" <ben@...adent.org.uk>,
	"decot@...glers.com" <decot@...glers.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	"andi@...stfloor.org" <andi@...stfloor.org>
Subject: RE: [RFC PATCH 00/30] Kernel NET policy



> On Mon, Jul 18, 2016 at 5:51 PM, Liang, Kan <kan.liang@...el.com> wrote:
> >
> >
> >> >
> >> > It is a big challenge to get good network performance. First, the
> >> > network performance is not good with default system settings.
> >> > Second, it is too difficult to do automatic tuning for all possible
> >> > workloads, since workloads have different requirements. Some
> >> > workloads may want
> >> high throughput.
> >>
> >> Seems you did lots of tests to find optimal settings for a given base policy.
> >>
> > Yes. Current test only base on Intel i40e driver. The optimal settings
> > should vary for other devices. But adding settings for new device is not
> hard.
> >
> The optimal settings are very dependent on system architecture (NUMA
> config, #cpus, memory, etc.) and sometimes kernel version as well. A
> database that provides best configurations across different devices,
> architectures, and kernel version might be interesting; but beware that that is
> a whole bunch of work to maintain, Either way policy like this really should
> be handled in userspace.

The expression "optimal" I used here is not accurate. Sorry for that.
The NET policy tries to get good (near optimal) performance by very
simple configuration.
I agree that there are lots of dependencies for the optimal settings.
But most of the settings should be very similar. The near optimal performance
by applying those common settings are good enough for most users. 
We don't need to maintain a database for configurations across
devices/architectures/kernel version...

Thanks,
Kan