From: Arnd Bergmann <arnd@arndb.de>
To: Wolfram Sang <w.sang@pengutronix.de>
Cc: Shawn Guo <shawn.guo@freescale.com>,
linux-mmc@vger.kernel.org, cjb@laptop.org,
linux@arm.linux.org.uk, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3] mmc: mxs-mmc: add mmc host driver for i.MX23/28
Date: Tue, 22 Feb 2011 17:15:07 +0100 [thread overview]
Message-ID: <201102221715.07480.arnd@arndb.de> (raw)
In-Reply-To: <20110222103349.GA2755@pengutronix.de>
On Tuesday 22 February 2011, Wolfram Sang wrote:
> # mount -t vfat /dev/mmcblk0p1 /mnt
> # dd if=/mnt/test.dat of=/tmp/a bs=1024
> # umount /mnt
> # ./dd --version
> dd (coreutils) 8.5
In general, you should try to rule out file system, garbage collection,
partitioning and cache effects.
With coreutils dd, a good command is
dd if=/dev/zero of=/dev/mmcblk0 bs=64K count=64 seek=256 oflag=direct
* Always write multiples of 4 MB to avoid garbage collection
* smaller block sizes may be faster, so writing 64 times 64K may
be better than writing 4 MB once, depending on the card
* don't write to the FAT area, so start writing at 16 MB into the
device.
* use direct I/O to bypass the page cache.
* read from /dev/zero instead of a disk file to avoid measuring the
wrong thing
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3] mmc: mxs-mmc: add mmc host driver for i.MX23/28
Date: Tue, 22 Feb 2011 17:15:07 +0100 [thread overview]
Message-ID: <201102221715.07480.arnd@arndb.de> (raw)
In-Reply-To: <20110222103349.GA2755@pengutronix.de>
On Tuesday 22 February 2011, Wolfram Sang wrote:
> # mount -t vfat /dev/mmcblk0p1 /mnt
> # dd if=/mnt/test.dat of=/tmp/a bs=1024
> # umount /mnt
> # ./dd --version
> dd (coreutils) 8.5
In general, you should try to rule out file system, garbage collection,
partitioning and cache effects.
With coreutils dd, a good command is
dd if=/dev/zero of=/dev/mmcblk0 bs=64K count=64 seek=256 oflag=direct
* Always write multiples of 4 MB to avoid garbage collection
* smaller block sizes may be faster, so writing 64 times 64K may
be better than writing 4 MB once, depending on the card
* don't write to the FAT area, so start writing at 16 MB into the
device.
* use direct I/O to bypass the page cache.
* read from /dev/zero instead of a disk file to avoid measuring the
wrong thing
Arnd
next prev parent reply other threads:[~2011-02-22 16:15 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-21 10:35 [PATCH v3] mmc: mxs-mmc: add mmc host driver for i.MX23/28 Shawn Guo
2011-02-21 10:35 ` Shawn Guo
2011-02-21 17:40 ` Wolfram Sang
2011-02-21 17:40 ` Wolfram Sang
2011-02-22 8:09 ` Shawn Guo
2011-02-22 8:09 ` Shawn Guo
2011-02-24 13:48 ` Shawn Guo
2011-02-24 13:48 ` Shawn Guo
2011-02-22 8:52 ` Shawn Guo
2011-02-22 8:52 ` Shawn Guo
2011-02-22 10:33 ` Wolfram Sang
2011-02-22 10:33 ` Wolfram Sang
2011-02-22 11:50 ` Shawn Guo
2011-02-22 11:50 ` Shawn Guo
2011-02-22 11:57 ` Wolfram Sang
2011-02-22 11:57 ` Wolfram Sang
2011-02-22 16:15 ` Arnd Bergmann [this message]
2011-02-22 16:15 ` Arnd Bergmann
2011-02-22 16:36 ` Wolfram Sang
2011-02-22 16:36 ` Wolfram Sang
2011-02-22 15:26 ` Chris Ball
2011-02-22 15:26 ` Chris Ball
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