From: "David S. Miller" <davem@redhat.com>
To: saw@saw.sw.com.sg
Cc: fxzhang@ict.ac.cn, linux-mips@oss.sgi.com,
linux-kernel@vger.kernel.org, netdev@oss.sgi.com,
jgarzik@mandrakesoft.com
Subject: Re: NAPI for eepro100
Date: Thu, 13 Jun 2002 01:47:00 -0700 (PDT) [thread overview]
Message-ID: <ae9mlg$n5l$2@main.gmane.org> (raw)
In-Reply-To: <20020613125753.A23693@castle.nmd.msu.ru>
From: Andrey Savochkin <saw@saw.sw.com.sg>
Date: Thu, 13 Jun 2002 12:57:53 +0400
On Wed, Jun 12, 2002 at 04:05:32PM -0700, David S. Miller wrote:
> No, it's worse than that.
>
> See how non-consistent memory is used by the eepro100 driver
> for descriptor bits? The skb->tail bits?
>
> That is very problematic.
What's the problem?
If it isn't allowed to do, then what is the meaning of PCI_DMA_BIDIRECTIONAL
mappings?
It's slow. Not wrong, just inefficient.
Descriptors were meant to be done using consistent mappings, not
"pci_map_*()"'d memory. The latter is meant to be used for long
linear DMA transfers to/from the device. It is not meant for things
the cpu pokes small bits of data in and out of, that is what
consistent DMA memory is for.
next prev parent reply other threads:[~2002-06-13 8:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3D0740ED.2060907@ict.ac.cn>
2002-06-12 23:00 ` NAPI for eepro100 Jeff Garzik
[not found] ` <3D07D270.5060902@mandrakesoft.com>
2002-06-12 23:05 ` David S. Miller
[not found] ` <20020612.160532.134201977.davem@redhat.com>
2002-06-12 23:17 ` Jeff Garzik
[not found] ` <3D07D6A6.7090308@mandrakesoft.com>
2002-06-12 23:33 ` David S. Miller
[not found] ` <20020613125753.A23693@castle.nmd.msu.ru>
2002-06-13 8:47 ` David S. Miller [this message]
2002-06-13 8:57 ` Andrey Savochkin
[not found] <20020612.163344.31410429.davem@redhat.com>
2002-06-13 2:25 ` Donald Becker
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