netdev - Re: [RFC PATCH 0/3] Simplified 16 bit Toeplitz hash algorithm

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Date:	Tue, 04 Jan 2011 15:43:07 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Alexander Duyck <alexander.h.duyck@...el.com>,
	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [RFC PATCH 0/3] Simplified 16 bit Toeplitz hash algorithm

On Mon, 2011-01-03 at 19:25 -0800, Tom Herbert wrote:
> >> The general idea is to at least keep the traffic local to one TX/RX
> >> queue pair so that if we cannot match the queue pair to the application,
> >> perhaps the application can be affinitized to match up with the queue
> >> pair.  Otherwise we end up with traffic getting routed to one TX queue
> >> on one CPU, and the RX being routed to another queue on perhaps a
> >> different CPU and it becomes quite difficult to match up the queues and
> >> the applications.
> >
> > Right.  That certainly seems like a Good Thing, though I believe it can
> > be implemented generically by recording the RX queue number on the
> > socket:
> >
> > http://article.gmane.org/gmane.linux.network/158477
> >
> I still don't see the value in doing this RX/TX queue pairing (unless
> you're considering the possibility of explicitly binding sockets to
> queue pairs).

Sure, the real value is in getting TX completions to line up with TX
initiation and queue pairing is not a reliable way to do that.

> XPS should be sufficient mechanism to get affinity on
> sending side.
[...]

At least if it's configured properly... or if this is automated using my
irq_cpu_rmap.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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