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From: Eliezer Tamir <eliezer.tamir@linux.intel.com>
To: Eric Dumazet <eric.dumazet@gmail.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>,
	Andi Kleen <andi@firstfloor.org>, HPA <hpa@zytor.com>,
	Eilon Greenstien <eilong@broadcom.com>,
	Or Gerlitz <or.gerlitz@gmail.com>,
	Alex Rosenbaum <alexr@mellanox.com>,
	Eliezer Tamir <eliezer@tamir.org.il>
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	[thread overview]
Message-ID: <51A60A42.20905@linux.intel.com> (raw)
In-Reply-To: <1369834647.5109.15.camel@edumazet-glaptop>

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

WARNING: multiple messages have this Message-ID (diff)
From: Eliezer Tamir <eliezer.tamir@linux.intel.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
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>
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	[thread overview]
Message-ID: <51A60A42.20905@linux.intel.com> (raw)
In-Reply-To: <1369834647.5109.15.camel@edumazet-glaptop>

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

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  parent reply	other threads:[~2013-05-29 14:02 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-29  6:39 [PATCH v6 net-next 0/5] net: low latency Ethernet device polling Eliezer Tamir
2013-05-29  6:39 ` [PATCH v6 net-next 1/5] net: add napi_id and hash Eliezer Tamir
2013-05-29  6:39   ` Eliezer Tamir
2013-05-29 12:56   ` Eric Dumazet
2013-05-29 13:09     ` David Laight
2013-05-29 13:09       ` David Laight
2013-05-29 13:43       ` Eric Dumazet
2013-05-29 13:43         ` Eric Dumazet
2013-05-29 15:04     ` Eliezer Tamir
2013-05-29 20:09   ` Ben Hutchings
2013-05-29 20:09     ` Ben Hutchings
2013-05-30  6:51     ` Eliezer Tamir
2013-05-30  6:51       ` Eliezer Tamir
2013-05-29  6:39 ` [PATCH v6 net-next 2/5] net: implement support for low latency socket polling Eliezer Tamir
2013-05-29  6:39   ` Eliezer Tamir
2013-05-29 13:37   ` Eric Dumazet
2013-05-29 13:37     ` Eric Dumazet
2013-05-29 13:42     ` David Laight
2013-05-29 13:42       ` David Laight
2013-05-29 13:48       ` Eric Dumazet
2013-05-29 13:48         ` Eric Dumazet
2013-05-29 14:01     ` Eliezer Tamir [this message]
2013-05-29 14:01       ` Eliezer Tamir
2013-05-29 14:20       ` yaniv saar
2013-05-29 15:01         ` Eliezer Tamir
2013-05-29 14:14   ` Or Gerlitz
2013-05-29 14:14     ` Or Gerlitz
2013-05-29 14:40     ` yaniv saar
2013-05-29 14:59     ` Eliezer Tamir
2013-05-29 14:59       ` Eliezer Tamir
2013-05-29 18:52       ` Or Gerlitz
2013-05-29 18:52         ` Or Gerlitz
2013-05-29 19:08         ` Eric Dumazet
2013-05-29 19:08           ` Eric Dumazet
2013-05-30  5:58           ` Eliezer Tamir
2013-05-30  5:58             ` Eliezer Tamir
2013-05-30  6:04         ` Eliezer Tamir
2013-05-30  6:04           ` Eliezer Tamir
2013-05-29 20:20     ` Ben Hutchings
2013-05-29 20:20       ` Ben Hutchings
2013-05-29  6:39 ` [PATCH v6 net-next 3/5] tcp: add TCP support for low latency receive poll Eliezer Tamir
2013-05-29  6:39   ` Eliezer Tamir
2013-05-29 13:38   ` Eric Dumazet
2013-05-29 13:38     ` Eric Dumazet
2013-05-29  6:39 ` [PATCH v6 net-next 4/5] ixgbe: Add support for ndo_ll_poll Eliezer Tamir
2013-05-29  6:39   ` Eliezer Tamir
2013-05-29  6:40 ` [PATCH v6 net-next 5/5] ixgbe: add extra stats " Eliezer Tamir
2013-05-29  6:40   ` Eliezer Tamir

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