Chris,
Do you think that lowering the controller speed to 50Mhz in case we have a
failure is a better idea than reducing the speed for all e823 ricoh
controllers? I can send a V2 of the patch. What do you think ?
On Wed, 13 Jul 2011, Arnd Bergmann wrote:
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
--
====================
Manoj Iyer
Ubuntu/Canonical
Hardware Enablement
====================
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