netdev - Re: [PATCH RFC 1/1] usb: Tell xhci when usb data might be misaligned

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Date:	Sat, 1 Feb 2014 22:18:42 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Mark Lord <mlord@...ox.com>
Cc:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Bjørn Mork <bjorn@...k.no>,
	David Laight <David.Laight@...lab.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	David Miller <davem@...emloft.net>,
	Dan Williams <dan.j.williams@...el.com>,
	"Nyman, Mathias" <mathias.nyman@...el.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Freddy Xin <freddy@...x.com.tw>
Subject: Re: [PATCH RFC 1/1] usb: Tell xhci when usb data might be misaligned

On Sat, Feb 1, 2014 at 9:30 PM, Mark Lord <mlord@...ox.com> wrote:
> On 14-02-01 02:54 AM, Ming Lei wrote:
> ..
>> With SG enabled, for the iperf client test case, the average urb size
>> for transmission will be increased from ~1500 to ~20K bytes in my
>> test case:
>>
>>    iperf -c $SRV -t 30 -P 4 -w 128K
>>
>> So I am wondering you guys do not care the improvement ..
>
> No, that's not it.  Simply, the recent changes killed the driver

I just want to clarify the sg approach does improve performance,
instead of no improvement mentioned by your guys.

> for some users, something Linus calls a "regression", and does not permit.

Even real regressions are easily/often introduced, and we are discussing
how to fix that. I suggest to unset the flag only for the known buggy
controllers.


Thanks,
--
Ming Lei
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