Message-ID: <1370445606.24311.265.camel@edumazet-glaptop>
Subject: Re: [PATCH v9 net-next 5/7] net: simple poll/select low latency
 socket poll
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Cc: David Miller <davem@davemloft.net>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Don Skidmore <donald.c.skidmore@intel.com>,
        e1000-devel@lists.sourceforge.net,
        Willem de Bruijn <willemb@google.com>,
        Ben Hutchings <bhutchings@solarflare.com>,
        Andi Kleen <andi@firstfloor.org>, HPA <hpa@zytor.com>,
        Eilon Greenstien <eilong@broadcom.com>,
        Or Gerlitz <or.gerlitz@gmail.com>, Amir Vadai <amirv@mellanox.com>,
        Eliezer Tamir <eliezer@tamir.org.il>
Date: Wed, 05 Jun 2013 08:20:06 -0700
In-Reply-To: <51AF401C.2030506@linux.intel.com>
References: <20130605103400.11172.49099.stgit@ladj378.jer.intel.com>
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On Wed, 2013-06-05 at 16:41 +0300, Eliezer Tamir wrote:
> On 05/06/2013 16:30, Eric Dumazet wrote:

> > I am a bit uneasy with this one, because an applicatio polling() on one
> > thousand file descriptors using select()/poll(), will call sk_poll_ll()
> > one thousand times.
> 
> But we call sk_poll_ll() with nonblock set, so it will only test once
> for each socket and not loop.
> 
> I think this is not as bad as it sounds.
> We still honor the time limit on how long to poll.

We still call ndo_ll_poll() a thousand times, and probably do a
spinlock/unlock a thousand times in the driver.

I would definitely be convinced if you give us some performance numbers
of a poll() on a thousand tcp sockets for example.

See my following mail about sk_poll_ll()

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