netdev - RE: about tx_queue_len for phonet driver

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Message-ID: <81C3A93C17462B4BBD7E272753C105791FB10F99BD@EXDCVYMBSTM005.EQ1STM.local>
Date:	Thu, 12 Jan 2012 12:24:40 +0100
From:	Hemant-vilas RAMDASI <hemant.ramdasi@...ricsson.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Rémi Denis-Courmont 
	<remi.denis-courmont@...ia.com>
Subject: RE: about tx_queue_len for phonet driver



> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> Sent: Thursday, January 12, 2012 4:28 PM
> To: Hemant-vilas RAMDASI
> Cc: netdev@...r.kernel.org; Rémi Denis-Courmont
> Subject: Re: about tx_queue_len for phonet driver
> 
> Le jeudi 12 janvier 2012 à 11:45 +0100, Hemant-vilas RAMDASI a écrit :
> > Hi,
> >
> > Can anyone guide me about when should a network driver set
> > tx_queue_len to 0?
> > We are facing a network congestion issue with phonet packets where
> one
> > of the control message packet is dropped because of congestion. In
> our
> > phonet network driver the tx_queue_len is set to 3 (taken from
> > usb-phonet mostly). If phonet cannot handle packet-drop (for pipe
> > messages), then should network driver always set tx_queue_len as 0?
> 
> 0 is usually used by virtual devices, since real device has a queue.
> 
> In your case, I would rather increase a bit the tx_queue_len
> 
> I noticed in the past 3 is the default for ppp, and we can indeed have
> drops because 3 is too small for current usages.
> 
> 
What happens if it is set to 0? Is it something like infinite queue where packet is never dropped?
I see many drivers (mainly IPC) using 0. 

Thanks & Regards,
Hemant