From: David Miller <davem@davemloft.net>
To: mcarlson@broadcom.com
Cc: netdev@vger.kernel.org, andy@greyhouse.net, mchan@broadcom.com
Subject: Re: [PATCH 10/13] tg3: Increase the PCI MRRS
Date: Mon, 12 Nov 2007 21:21:35 -0800 (PST) [thread overview]
Message-ID: <20071112.212135.172019737.davem@davemloft.net> (raw)
In-Reply-To: <1194655141.5745.272.camel@teletran1>
From: "Matt Carlson" <mcarlson@broadcom.com>
Date: Fri, 09 Nov 2007 16:39:01 -0800
> Previous devices hardcoded the PCI Maximum Read Request Size to 4K. To
> better comply with the PCI spec, the hardware now defaults the MRRS to
> 512 bytes. This will yield poor driver performance if left untouched.
> This patch increases the MRRS to 4K on driver initialization.
>
> Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
> Signed-off-by: Michael Chan <mchan@broadcom.com>
I've applied this patch, but...
I sense that the PCI spec wants devices to use an MRRS value of 512 in
order to get better fairness on a PCI-E segment amongst multiple
devices.
>From that perspective, jacking up the MRRS to 4096 unilaterally seems
like a very bad idea. If this was necessary for good performance, I'm
sure the PCI spec folks would have choosen a higher value.
Or is this some tg3 specific performance issue?
next prev parent reply other threads:[~2007-11-13 5:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-10 0:39 [PATCH 10/13] tg3: Increase the PCI MRRS Matt Carlson
2007-11-13 5:21 ` David Miller [this message]
2007-11-15 22:20 ` Matt Carlson
2007-11-15 22:41 ` David Miller
2007-11-15 23:51 ` Michael Chan
2007-11-15 23:08 ` David Miller
2007-11-16 0:32 ` Rick Jones
2007-11-16 2:17 ` Michael Chan
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