From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Clemens Ladisch <clemens@ladisch.de>,
Greg Kroah-Hartman <gregkh@suse.de>,
Sarah Sharp <sarah.a.sharp@linux.intel.com>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: fix number of mapped SG DMA entries
Date: Thu, 15 Dec 2011 17:22:53 +0100 [thread overview]
Message-ID: <4EEA1EDD.9000609@linutronix.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1112151058090.1644-100000@iolanthe.rowland.org>
On 12/15/2011 05:01 PM, Alan Stern wrote:
>> Is there anything special you do to get into this kind of situation?
>> Like 16GiB of memory on 32bit with highmem and a brutal disk/io test
>> case so?
>
> As I understand it, the typical case is that two SG entries in a row
> refer to adjacent pages of physical memory. The mapping routine then
> collapses them into a single entry referring to all the pages.
>
> However, this is not the sort of thing you can deliberately cause,
> unless you set up your SG list by hand.
Thanks, both of you for the explanation.
>
> Alan Stern
Sebastian
prev parent reply other threads:[~2011-12-15 16:23 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-03 22:41 [PATCH] usb: fix number of mapped SG DMA entries Clemens Ladisch
2011-12-04 16:59 ` Alan Stern
2011-12-04 17:04 ` Clemens Ladisch
2011-12-15 12:39 ` Sebastian Andrzej Siewior
2011-12-15 15:37 ` Clemens Ladisch
2011-12-15 16:01 ` Alan Stern
2011-12-15 16:22 ` Sebastian Andrzej Siewior [this message]
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