From: Edward Cree <ecree@solarflare•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: <netdev@vger•kernel.org>, Shawn Bohrer <shawn.bohrer@gmail•com>,
"Shawn Bohrer" <sbohrer@rgmadvisors•com>,
Jonathan Cooper <jcooper@solarflare•com>
Subject: Re: [RFC PATCH] udp: allow busy_poll on some unconnected sockets
Date: Thu, 10 Apr 2014 19:38:24 +0100 [thread overview]
Message-ID: <5346E520.7080007@solarflare.com> (raw)
In-Reply-To: <1397154745.16584.42.camel@edumazet-glaptop2.roam.corp.google.com>
On 10/04/14 19:32, Eric Dumazet wrote:
> On Thu, 2014-04-10 at 19:04 +0100, Edward Cree wrote:
>
>> Tested by setting IFF_SINGLE_NAPI in sfc; a UDP ping-pong test showed a
>> performance benefit from sysctl net.core.busy_{read,poll}=50 in both the
>> connected and unconnected case, where previously it only saw the benefit
>> when the socket had been connected.
> Right, but how often do we have single NAPI devices on hosts wanting
> very low latencies ?
>
Well, sfc only has a single NAPI context per device, and I'm fairly sure
most sfc users want very low latencies.
Or have I misunderstood?
(Note that it doesn't matter if there are other NAPI-using devices on
the host, since the socket is bound to a local address and thus is only
going to receive packets from the one device that has that address. So
maybe IFF_SINGLE_NAPI is a bad name and it should be
IFF_DEVICE_ONLY_HAS_A_SINGLE_NAPI_CONTEXT. But that's a bit unwieldy ;)
next prev parent reply other threads:[~2014-04-10 18:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-09 14:13 udp: Question about busy_poll change Edward Cree
2014-04-09 14:51 ` Shawn Bohrer
2014-04-09 16:20 ` Edward Cree
2014-04-10 18:04 ` [RFC PATCH] udp: allow busy_poll on some unconnected sockets Edward Cree
2014-04-10 18:32 ` Eric Dumazet
2014-04-10 18:38 ` Edward Cree [this message]
2014-04-10 19:04 ` Eric Dumazet
2014-04-11 10:44 ` Jonathan Cooper
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