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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Michael Grzeschik <mgr@pengutronix.de>
Cc: Dan Vacura <w36195@motorola.com>,
	linux-usb@vger.kernel.org,
	Daniel Scally <dan.scally@ideasonboard.com>,
	Thinh Nguyen <Thinh.Nguyen@synopsys.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Felipe Balbi <balbi@kernel.org>,
	Paul Elder <paul.elder@ideasonboard.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v2 0/3] uvc gadget performance issues
Date: Tue, 11 Oct 2022 21:53:48 +0200	[thread overview]
Message-ID: <Y0XJzGW/zlcCfffi@kroah.com> (raw)
In-Reply-To: <20221011194808.GH27626@pengutronix.de>

On Tue, Oct 11, 2022 at 09:48:08PM +0200, Michael Grzeschik wrote:
> I also have an patch in the queue that will limit the sg support for
> devices with speed > HIGH_SPEED. Because of the overhead of the limited
> transfer payload of 1024*3 Bytes, it is possible that a simple memcpy
> will actually be fast enough. But for that patch I still have to make
> proper measurements. Btw. which USB speed are you transferring with?

For a payload that small, yes a memcpy is almost always faster.  I think
it's only much larger sizes that actually start to help with sg.

Can you submit this change now?  Odds are it will help out a lot of
systems.

thanks,

greg k-h

  reply	other threads:[~2022-10-11 20:06 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-11 18:34 [PATCH v2 0/3] uvc gadget performance issues Dan Vacura
2022-10-11 18:34 ` [PATCH v2 1/3] usb: gadget: uvc: make interrupt skip logic configurable Dan Vacura
2022-10-12 20:44   ` Dan Vacura
2022-10-11 18:34 ` [PATCH v2 2/3] usb: gadget: uvc: fix sg handling in error case Dan Vacura
2022-10-11 18:34 ` [PATCH v2 3/3] usb: gadget: uvc: add configfs option for sg support Dan Vacura
2022-10-11 19:48 ` [PATCH v2 0/3] uvc gadget performance issues Michael Grzeschik
2022-10-11 19:53   ` Greg Kroah-Hartman [this message]
2022-10-11 20:16   ` Dan Vacura

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