First access to mounted jffs2 partition is slow

First access to mounted jffs2 partition is slow

[Will Wagner]

Hello,

I have an ARM11 system with a JFFS2 partition in NAND flash. It works 
but the first time it is accessed after mounting it can be very slow.

These are the steps I am performing:

# flash_eraseall /dev/mtd4
Erasing 128 Kibyte @ 5fe0000 -- 99 % complete.
# time mount /dev/mtdblock4 /flash -t jffs2
real    0m 1.25s
user    0m 0.01s
sys     0m 0.13s
# time ls flash		- with an empty filsystem, this takes no time
real    0m 0.00s
user    0m 0.01s
sys     0m 0.00s
# cp /sdcard/bigfile flash/	- bigfile is ~8MB
# umount /flash
# time mount /dev/mtdblock4 /flash -t jffs2
real    0m 2.63s
user    0m 0.01s
sys     0m 0.50s
# time ls flash		- first time we do this it takes a long time
bigfile
real    0m 11.79s
user    0m 0.00s
sys     0m 0.18s
# time ls flash		- subsequent reads are fast
bigfile
real    0m 0.00s
user    0m 0.01s
sys     0m 0.00s


It was my understanding that the only slow step should be mounting the 
partition when it checks the entire filesystem. Is that correct? Is it 
normal that the first file operation on the partition is slow and then 
all others are fast? That the mount is slow is not a problem but would 
be good if we could make the first access faster even if it means the 
mount must get slower.

This is using Linux 2.6.19.2 with uClibc 0.9.29, busybox 1.9.0 and 
mtd-utils 1.1.0

Thanks,

Will.

-- 
------------------------------------------------------------------------
Will Wagner                                     will_wagner@carallon.com
Senior Project Engineer                  Office Tel: +44 (0)20 7371 2032
Carallon Ltd, Studio G20, Shepherds Building, Rockley Rd, London W14 0DA
------------------------------------------------------------------------

Re: First access to mounted jffs2 partition is slow

[Matthieu CASTET]

Hi,

Will Wagner wrote:
> Hello,
> 
> I have an ARM11 system with a JFFS2 partition in NAND flash. It works 
> but the first time it is accessed after mounting it can be very slow.
I had a similar problem on ARM9 (see 
http://thread.gmane.org/gmane.linux.drivers.mtd/20340/focus=20355 )



Matthieu


-- 
Matthieu Castet
Ingénieur Développement Logiciel
Parrot SA
174 Quai de Jemmapes
75010 Paris, France

Tél: +33 (0) 1 48 03 74 78
Fax: +33 (0) 1 48 03 06 66
Email: matthieu.castet@parrot.fr
http://www.parrot.biz

Re: First access to mounted jffs2 partition is slow

[DMcLeod]

Will Wagner wrote:
> Hello,
>
> I have an ARM11 system with a JFFS2 partition in NAND flash. It works 
> but the first time it is accessed after mounting it can be very slow.
>
> These are the steps I am performing:
>
> # flash_eraseall /dev/mtd4
> Erasing 128 Kibyte @ 5fe0000 -- 99 % complete.
> # time mount /dev/mtdblock4 /flash -t jffs2
> real    0m 1.25s
> user    0m 0.01s
> sys     0m 0.13s
> # time ls flash		- with an empty filsystem, this takes no time
> real    0m 0.00s
> user    0m 0.01s
> sys     0m 0.00s
> # cp /sdcard/bigfile flash/	- bigfile is ~8MB
> # umount /flash
> # time mount /dev/mtdblock4 /flash -t jffs2
> real    0m 2.63s
> user    0m 0.01s
> sys     0m 0.50s
> # time ls flash		- first time we do this it takes a long time
> bigfile
> real    0m 11.79s
> user    0m 0.00s
> sys     0m 0.18s
> # time ls flash		- subsequent reads are fast
> bigfile
> real    0m 0.00s
> user    0m 0.01s
> sys     0m 0.00s
>
>
> It was my understanding that the only slow step should be mounting the 
> partition when it checks the entire filesystem. Is that correct? Is it 
> normal that the first file operation on the partition is slow and then 
> all others are fast? That the mount is slow is not a problem but would 
> be good if we could make the first access faster even if it means the 
> mount must get slower.
>
> This is using Linux 2.6.19.2 with uClibc 0.9.29, busybox 1.9.0 and 
> mtd-utils 1.1.0
>
> Thanks,
>
> Will.
>
>   

We fought that same exact problem for some time. It turned out being 
that we had set the verbosity (something like FS_JFFS2_DEBUG=2) to the 
highest setting. It literally took 30s or more to do an 'ls' the first 
time.

HTH


--------------------------------------------------
Dennis McLeod
dmcleod@bittware.com
http://www.bittware.com
(603) 226 0404 x514
--------------------------------------------------

Re: First access to mounted jffs2 partition is slow

[michael]

Hi,
> Will Wagner wrote:
>   
>> Hello,
>>
>> I have an ARM11 system with a JFFS2 partition in NAND flash. It works 
>> but the first time it is accessed after mounting it can be very slow.
>>
>> These are the steps I am performing:
>>
>> # flash_eraseall /dev/mtd4
>> Erasing 128 Kibyte @ 5fe0000 -- 99 % complete.
>> # time mount /dev/mtdblock4 /flash -t jffs2
>> real    0m 1.25s
>> user    0m 0.01s
>> sys     0m 0.13s
>> # time ls flash		- with an empty filsystem, this takes no time
>> real    0m 0.00s
>> user    0m 0.01s
>> sys     0m 0.00s
>> # cp /sdcard/bigfile flash/	- bigfile is ~8MB
>> # umount /flash
>> # time mount /dev/mtdblock4 /flash -t jffs2
>> real    0m 2.63s
>> user    0m 0.01s
>> sys     0m 0.50s
>> # time ls flash		- first time we do this it takes a long time
>> bigfile
>> real    0m 11.79s
>> user    0m 0.00s
>> sys     0m 0.18s
>> # time ls flash		- subsequent reads are fast
>> bigfile
>> real    0m 0.00s
>> user    0m 0.01s
>> sys     0m 0.00s
>>
>>     
I think that is a problem of jffs2 and I think that is related to the 
time spent during the fstat64 system but
I'm not sure. I have little experince with jffs2.

Regards Michael