From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751360Ab1HVLWH (ORCPT ); Mon, 22 Aug 2011 07:22:07 -0400 Received: from na3sys009aog101.obsmtp.com ([74.125.149.67]:57850 "EHLO na3sys009aog101.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751022Ab1HVLWA (ORCPT ); Mon, 22 Aug 2011 07:22:00 -0400 Date: Mon, 22 Aug 2011 14:21:54 +0300 From: Felipe Balbi To: Per Forlin Cc: Felipe Balbi , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linaro-dev@lists.linaro.org, Michal Nazarewicz , Alan Stern , Greg Kroah-Hartman Subject: Re: [PATCH v6] usb: gadget: storage: make FSG_NUM_BUFFERS variable size Message-ID: <20110822112153.GA30398@legolas.emea.dhcp.ti.com> Reply-To: balbi@ti.com References: <1313781687-13955-1-git-send-email-per.forlin@linaro.org> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="UugvWAfsgieZRqgk" Content-Disposition: inline In-Reply-To: <1313781687-13955-1-git-send-email-per.forlin@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --UugvWAfsgieZRqgk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Fri, Aug 19, 2011 at 09:21:27PM +0200, Per Forlin wrote: > FSG_NUM_BUFFERS is set to 2 as default. > Usually 2 buffers are enough to establish a good buffering pipeline. > The number may be increased in order to compensate a for bursty VFS > behaviour. >=20 > Here follows a description of system that may require more than > 2 buffers. > * CPU ondemand governor active > * latency cost for wake up and/or frequency change > * DMA for IO >=20 > Use case description. > * Data transfer from MMC via VFS to USB. > * DMA shuffles data from MMC and to USB. > * The CPU wakes up every now and then to pass data in and out from VFS, > which cause the bursty VFS behaviour. >=20 > Test set up > * Running dd on the host reading from the mass storage device > * cmdline: dd if=3D/dev/sdb of=3D/dev/null bs=3D4k count=3D$((256*100)) > * Caches are dropped on the host and on the device before each run >=20 > Measurements on a Snowball board with ondemand_governor active. >=20 > FSG_NUM_BUFFERS 2 > 104857600 bytes (105 MB) copied, 5.62173 s, 18.7 MB/s > 104857600 bytes (105 MB) copied, 5.61811 s, 18.7 MB/s > 104857600 bytes (105 MB) copied, 5.57817 s, 18.8 MB/s >=20 > FSG_NUM_BUFFERS 4 > 104857600 bytes (105 MB) copied, 5.26839 s, 19.9 MB/s > 104857600 bytes (105 MB) copied, 5.2691 s, 19.9 MB/s > 104857600 bytes (105 MB) copied, 5.2711 s, 19.9 MB/s >=20 > There may not be one optimal number for all boards. This is why > the number is added to Kconfig. If selecting USB_GADGET_DEBUG_FILES > this value may be set by a module parameter as well. >=20 > Signed-off-by: Per Forlin applied, thanks. --=20 balbi --UugvWAfsgieZRqgk Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQEcBAEBAgAGBQJOUjvRAAoJEAv8Txj19kN1gAAIAJ7EY2l+E0ucdMc5iAXEP6Y/ 5NtnAOyA9Qec1OZO0+CcgPJpbYLTj49WFD161F8UqIMOYPVyCtasK5OG4uIKMQOY o6CoCGAWFTzpvCyw6ZhQsa9hilUNVTKD5Ti1AehvyrZRmBIf+pOB/7zEUFQeU0Hj 6f1v2jImjnK6TckW+QBAu94rdpWT4+BA9V7HbRcg2W+VmkK2T4VdEzRFvPHUfYA1 oMg3KxkOl8qo5ZEh9WgIU4o7j53cd4xKd/vUprNbJ19Iy9rH0JZazxDAZQAOnr1m aJbQZzT9SwpGhjYaCWrWRIP7rR8aYF77lO8h9inPSk5A0BwcTq9WpwWlgAXN1qY= =qbpZ -----END PGP SIGNATURE----- --UugvWAfsgieZRqgk--