JFFS2 errors on ppc-4xx with CFI NOR flash

[Ryan Thompson]

I also created the attached gnuplot graph showing the time taken to
write 128KiB files versus the filesystem utilization. Note that the
underlying partition size is 32128KiB.

In case attachments don't work on linux-mtd, the graph is also hosted
at http://ry.ca/clients/jffs2-128KiB.png

- R

On Fri, Mar 5, 2010 at 11:36 AM, Ryan Thompson <i at ry.ca> wrote:
> On Fri, Mar 5, 2010 at 3:56 AM, massimo cirillo <maxcir at gmail.com> wrote:
>> I suppose you don't have CONFIG_MTD_XIP enabled.
>> So in order to completely disable the suspend,
>> please in chip_ready() function just after "case FL_ERASING:"
>> (line 775) put the line "goto sleep;" and repeat your test.
>> Let me know.
>
> By skipping the FL_ERASING case as you suggested, my test now
> completes successfully without any INFO-or-higher kernel messages.
>
> However, it still takes a very long time. The initial files are
> written out quickly (subjectively, performance seems similar to raw
> mtd speed). However, after 50% or so, performance begins to degrade
> dramatically. At 65%, a 256KiB file takes 11 sec to write. At 75%, 20
> sec. 90%, 38 sec. 95%, 77 sec. 99%, 121 sec. The entire test took 28.4
> minutes to go from 3%-100% on the ~32MiB partition.
>
> Performance seems somewhat consistent with my previous result:
>
>> 2010/3/4 Ryan Thompson <i at ry.ca>:
>>> The errors continued until the filesystem actually reported 100% full
>>> and my script terminated. The entire 3%-100% operation took about 21
>>> minutes for <32MiB, and was definitely much slower towards the end
>>> with all the errors.
>
> I've done a flash_eraseall -j followed by a reboot before each run.
>
> I also benchmarked the mtdblock performance without JFFS2 (also
> getting input from urandom):
>
> # time dd if=/dev/urandom of=/dev/mtdblock16
> dd: writing '/dev/mtdblock16': No space left on device
> 64257+0 records in
> 64256+0 records out
> Command exited with non-zero status 1
> real    5m 30.17s
> user    0m 0.08s
> sys     1m 2.66s
> # perl -le 'printf("bytes written = 0x%08x\n", 64256 * 512);'
> bytes written = 0x01f60000
> # grep modules /proc/mtd
> mtd16: 01f60000 00020000 "modules"
>
> - R
>
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