linux-kernel - Re: e1000 driver 2.6.18 - how to waste processor cycles

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Message-ID: <4807377b0611091445s11575f5ej15c7bf7126bb5658@mail.gmail.com>
Date:	Thu, 9 Nov 2006 14:45:34 -0800
From:	"Jesse Brandeburg" <jesse.brandeburg@...il.com>
To:	"Jeffrey V. Merkey" <jmerkey@...eranetworks.com>
Cc:	"Linux kernel" <linux-kernel@...r.kernel.org>,
	"NetDEV list" <netdev@...r.kernel.org>
Subject: Re: e1000 driver 2.6.18 - how to waste processor cycles

On 11/9/06, Jeffrey V. Merkey <jmerkey@...eranetworks.com> wrote:
> In the case I am referring to, the memory is already mapped with a
> previous call, which means it may be getting
> mapped twice.

I guess maybe I'm not keeping up with you.  This is what I see looking
in 2.6.18, i see e1000_clean_rx_irq:

check done bit
pci_unmap_single
copybreak and recycle
OR
hand buffer up stack

the only branch before the unmap is the napi break out, and in that
case we don't change any memory state, so alloc will not do anything.

As for alloc rx, we always map, because we always unmapped.

Did I miss something?  I would appreciate a more detailed explanation
of what you see going wrong.
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