From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH] mmc: Added quirks for Ricoh 1180:e823 lower base clock frequency Date: Wed, 13 Jul 2011 18:35:25 +0200 Message-ID: <201107131835.25217.arnd@arndb.de> References: <1310419715-13254-1-git-send-email-manoj.iyer@canonical.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Manoj Iyer Cc: Chris Ball , linux-kernel@vger.kernel.org, jbarnes@virtuousgeek.org, matsumur@nts.ricoh.co.jp, linux-pci@vger.kernel.org, linux-mmc@vger.kernel.org List-Id: linux-mmc@vger.kernel.org On Wednesday 13 July 2011, Manoj Iyer wrote: > > Chris/Arnd, > > Here is a series of test I did with the patched kernel. > == cold boot insert SD card == > u@u:~/flash/flashbench$ sudo ./flashbench -O --erasesize=$[4 * 1024 * > 1024] --blocksize=$[256 * 1024] /dev/mmcblk0 --open-au-nr=2 > 4MiB 4.96M/s > 2MiB 6.3M/s > 1MiB 6.23M/s > 512KiB 6.23M/s > 256KiB 6.26M/s The very first one obviously triggers a garbage collection. Everything after that is well within measuring accuracy around 6.25MB/s > On Wed, 13 Jul 2011, Chris Ball wrote: > > > > That makes sense. Do you think this explains Manoj getting a slower > > first file copy speed (757ms vs. 480ms) after applying his patch? > > (Manoj, perhaps you could retry your test without GC being needed?) Yes. For a single sample, it can easily explain differences up to 500ms. You have to average out file system benchmarks across a lot of files to be sure. > > What would we expect lowering the SD base clock frequency from 200MHz > > to 50MHz to do to performance theoretically? Not much. This card only has a 6MB/s write speed, which is well below what a 50 MHz bus can do. It mgiht be different on a fast eMMC device or a Sandisk Extreme Pro UHS-1 card. Arnd