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Date: Fri, 22 May 2009 08:27:00 +0800
Message-ID: <60ce8d250905211727m71f2d17eice895fa961d82e17@mail.gmail.com>
Subject: Re: Throughput is not changed when setting to a much higher bit rate
From: Dongas <dongas86@gmail.com>
To: Dan Williams <dcbw@redhat.com>
Cc: "John W. Linville" <linville@tuxdriver.com>,
	linux-wireless@vger.kernel.org
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2009/5/21 Dan Williams <dcbw@redhat.com>:
> On Wed, 2009-05-20 at 22:48 +0800, Dongas wrote:
>> 2009/5/20 John W. Linville <linville@tuxdriver.com>:
>> > On Wed, May 20, 2009 at 01:48:32AM +0800, Dongas wrote:
>> >
>> >> Why the bandwidth is not changed when bit rate is changed to 11Mb/s?
>> >> Any thing wrong?
>> >
>> > More errors at higher bit rate, resulting in more retries? ?Just a
>> > thought...
>> >
>> Is there a quick way to verify this possible reason? I'm using Libertas driver.
>>
>> BTW, my sdio host driver is using polling mode to handle SDIO IRQ.
>> Could this be the cause of such poor performance?
>
> Definitely. ?With libertas, the largest class of issues by *far* that
> we've seen are controller related. ?I seem to recall that I've pulled
> about 6Mbps through the card using a normal Ricoh controller from a
> Fujitsu laptop. ?I can recheck that.
>

Thanks for your info,Dan.
For Libertas driver , do you know which reason would be the cause of
the issue i encounterred?
Basically if i set the bit rate of Marvell card to a much higher value
such as 11Mb/s or even 48Mb/s, the HW should be capable of
transferring in hign bit rate.
However , the result from iperf indicates that the real bandwidth is
remain around 1.1Mbps, even no improvement.
It seems Marvell 8686 WiFi module will adjust the bit rate according
to the real situation.
So the bottleneck would be host side , HW or driver, right?
If there a way for me to debug this issue in libertas driver to find
out the root reason?
If the issue is related to our HW, we would like to take some
modifications on it.

>> (However I just can't believe the performance is so poor ,only around
>> 1.1Mbps, with polling mode of SDIO IRQ)
There must be something wrong.

Regards
Dongas