Re: [[v4] 2/5] MMC: Use CMD23 for multiblock transfers when we can.

[Andrei Warkentin <andreiw@motorola.com>]

On Mon, May 23, 2011 at 2:25 PM, Andrei Warkentin <andreiw@motorola.com> wrote:
> On Mon, May 23, 2011 at 7:40 AM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> Hi A..
>>
>> I tested your patch..(using CMD23)
>> my environment is the below.
>> eMMC card : Sandisk SEM8G (eMMC 4.3+)
>> buswidth : 4bit (SDR)
>> AP : C110
>> benchmark : IOzone
>>
>> I want to know how do you think about this result?
>> (i can't see your results)
>>
>
> I think that you should use my tool to measure I/O performance.
> Because I want to see the mins, maxes, average and
> std dev. Iozone adds way too much noise to the data. You can run it 5
> times in a row and get completely different numbers. Please use
> https://github.com/andreiw/superalign.
>
> For a more realistic test you can try performing 20000 sqlite inserts
> or something of the sort and timing that.
>
> A
>

Additionally, be careful how you do your testing. I don't want to
sound obvious, but, to ensure you can actually compare the collected
data against each other -
1) Disable all power/frequency scaling/management/gating, suspend/resume, etc.
2) Make sure nothing else uses the eMMC. No root mounted fs, nothing.
3) Make sure you are avoiding block cache and file system. You want
direct block I/O.
4) For extra extra extra reliable results - Make sure you are not
rebooting across testing. You will need to add a flag so you can
disable CMD23 on the fly via debugfs.

For sqlite testing some other helpful hints -
1) Unmount partition containing files on which the SQLite test operates.
2) Perform BLKDISCARD over the partition.
3) Format with desired file system.
4) Mount.
6) Sync && echo 3 > /proc/sys/vm/drop_caches
7) Perform test.
8) Umount.
9) Repeat from (1)

A