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From: Anton Blanchard <anton@samba.org>
To: Michael Chan <mchan@broadcom.com>
Cc: Matthew Carlson <mcarlson@broadcom.com>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"andy@greyhouse.net" <andy@greyhouse.net>
Subject: Re: [PATCH net-next 09/14] tg3: Improve small packet performance
Date: Thu, 5 Aug 2010 09:08:25 +1000	[thread overview]
Message-ID: <20100804230825.GQ29316@kryten> (raw)
In-Reply-To: <1280962049.7554.25.camel@HP1>

 
Hi,

> We generally only get an estimate of the available tx ring size when we
> call tg3_tx_avail(), so memory barriers are not generally needed.  We
> put a compiler barrier there to make sure that the compiler will fetch
> the tx_prod and tx_cons from memory to give us a better estimate.
> 
> In specific cases detailed in the patch description, we do need memory
> barriers when we call netif_tx_stop_queue() and then check for the tx
> ring.  We decided to put memory barriers exactly where they're needed
> instead of inside tg3_tx_avail() which is an overkill.

Thanks Matt and Michael. I was pretty sure you were thinking about
ordering issues but wanted to double check.

Anton

      reply	other threads:[~2010-08-04 23:13 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-02 21:26 [PATCH net-next 09/14] tg3: Improve small packet performance Matt Carlson
2010-08-04 22:27 ` Anton Blanchard
2010-08-04 22:46   ` Matt Carlson
2010-08-04 22:47   ` Michael Chan
2010-08-04 23:08     ` Anton Blanchard [this message]

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