From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Subject: Re: [PATCH v6 net-next 2/5] net: implement support
 for low latency socket polling
Date: Wed, 29 May 2013 17:01:38 +0300
Message-ID: <51A60A42.20905@linux.intel.com>
References: <20130529063916.27486.3841.stgit@ladj378.jer.intel.com>
	<20130529063935.27486.18610.stgit@ladj378.jer.intel.com>
	<1369834647.5109.15.camel@edumazet-glaptop>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Cc: Willem de Bruijn <willemb@google.com>, Or Gerlitz <or.gerlitz@gmail.com>,
	e1000-devel@lists.sourceforge.net, netdev@vger.kernel.org,
	HPA <hpa@zytor.com>, Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Alex Rosenbaum <alexr@mellanox.com>, linux-kernel@vger.kernel.org,
	Eliezer Tamir <eliezer@tamir.org.il>, Andi Kleen <andi@firstfloor.org>,
	Eilon Greenstien <eilong@broadcom.com>, David Miller <davem@davemloft.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Return-path: <e1000-devel-bounces@lists.sourceforge.net>
In-Reply-To: <1369834647.5109.15.camel@edumazet-glaptop>
List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/e1000-devel>,
	<mailto:e1000-devel-request@lists.sourceforge.net?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=e1000-devel>
List-Post: <mailto:e1000-devel@lists.sourceforge.net>
List-Help: <mailto:e1000-devel-request@lists.sourceforge.net?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/e1000-devel>,
	<mailto:e1000-devel-request@lists.sourceforge.net?subject=subscribe>
Errors-To: e1000-devel-bounces@lists.sourceforge.net
List-Id: netdev.vger.kernel.org

On 29/05/2013 16:37, Eric Dumazet wrote:
> On Wed, 2013-05-29 at 09:39 +0300, Eliezer Tamir wrote:

>> +static inline unsigned long ll_end_time(void)
>> +{
>> +	return TSC_MHZ * ACCESS_ONCE(sysctl_net_ll_poll) + get_cycles();
>> +}
>
> This can overflow.
>
> Multiply is giving 32bits, as tsc_khz is an int, and sysctl_net_ll_poll
> is an int.
>
> unsigned long sysctl_net_ll_poll ?
OK

> Also, if we want this to work on i386, the correct type to use for
> ll_end_time(void) would be cycles_t

OK
I would be really surprised if someone uses this on an i386, but I guess 
you never know.

Thanks!
-Eliezer

------------------------------------------------------------------------------
Introducing AppDynamics Lite, a free troubleshooting tool for Java/.NET
Get 100% visibility into your production application - at no cost.
Code-level diagnostics for performance bottlenecks with <2% overhead
Download for free and get started troubleshooting in minutes.
http://p.sf.net/sfu/appdyn_d2d_ap1
_______________________________________________
E1000-devel mailing list
E1000-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/e1000-devel
To learn more about Intel&#174; Ethernet, visit http://communities.intel.com/community/wired