Reduce boot time with jffs2 and CM-X255

Reduce boot time with jffs2 and CM-X255

[Michel LECONTE]

Hi,

I use a cm-x255 compulab card and I boot on the NAND flash with jffs2
filesystem.

My problem is the boot is too long.

My method to boot on the NAND flash is :

1) I boot on the cm-x225 via nfs.

2) I format the flash:

flash_eraseall -j /dev/mtd1

3) I mount the flash :

mount -t jffs2 /dev/mtdblock1 /mountpoint

4) I put the distribution of my system on the flash:

cp -r /Distribution/* /mountpoint

5) I unmount the flash :

umount /mountpoint

6) Finally, I boot on the cm-x255 board with the 2.6.18 kernel and
options are :

- Boot options : root=/dev/mtdblock1 rootfstype=jffs2
ip=192.168.82.70:::255.255.255.0:arm:eth0

- Miscellaneous filesystems : Journalling Flash File System v2 (JFFS2)
support

JFFS2 debugging verbosity à 0

JFFS2 write-buffering support

JFFS2 summary support (EXPERIMENTAL)


I would like to know what I'm missing or what I have to do to decrease
boot time ?


Thanks for any suggestion or help.

Michel

Re: Reduce boot time with jffs2 and CM-X255

[Enrico Migliore]

Hi Michel,

 could you be more specific?
 The boot time, in a production environment, is the time that elapses 
from the board reset to the login prompt.
 How long is that time on your cm-x255?

 Enrico
> Hi,
>
> I use a cm-x255 compulab card and I boot on the NAND flash with jffs2
> filesystem.
>
> My problem is the boot is too long.
>
> My method to boot on the NAND flash is :
>
> 1) I boot on the cm-x225 via nfs.
>
> 2) I format the flash:
>
> flash_eraseall -j /dev/mtd1
>
> 3) I mount the flash :
>
> mount -t jffs2 /dev/mtdblock1 /mountpoint
>
> 4) I put the distribution of my system on the flash:
>
> cp -r /Distribution/* /mountpoint
>
> 5) I unmount the flash :
>
> umount /mountpoint
>
> 6) Finally, I boot on the cm-x255 board with the 2.6.18 kernel and
> options are :
>
> - Boot options : root=/dev/mtdblock1 rootfstype=jffs2
> ip=192.168.82.70:::255.255.255.0:arm:eth0
>
> - Miscellaneous filesystems : Journalling Flash File System v2 (JFFS2)
> support
>
> JFFS2 debugging verbosity à 0
>
> JFFS2 write-buffering support
>
> JFFS2 summary support (EXPERIMENTAL)
>
>
> I would like to know what I'm missing or what I have to do to decrease
> boot time ?
>
>
> Thanks for any suggestion or help.
>
> Michel
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>
>   

Re: Reduce boot time with jffs2 and CM-X255

[Michel LECONTE]

Excuse me for the lack of informations.

I use a CM-X255 with a NAND Flash of 512 Mo
where roughly 250 Mo are used (90 Mo for the native distribution
provided by Compulab and 160 Mo for specific applications).

At the boot, there's a scanning of the MTD1 (4096 blocks) corresponding 
to the NAND Flash.
This scanning takes 1mn20s. The full boot time, from a reset to the 
login prompt, takes 4mn.
 
I hope that these precisions can be useful.

Thanks for any help or suggestion.


Michel


Enrico Migliore a écrit :
> Hi Michel,
>
> could you be more specific?
> The boot time, in a production environment, is the time that elapses 
> from the board reset to the login prompt.
> How long is that time on your cm-x255?
>
> Enrico
>
>

Re: Reduce boot time with jffs2 and CM-X255

[Artem Bityutskiy]

On Wed, 2006-12-20 at 09:38 +0100, Michel LECONTE wrote:
> Excuse me for the lack of informations.
> 
> I use a CM-X255 with a NAND Flash of 512 Mo
> where roughly 250 Mo are used (90 Mo for the native distribution
> provided by Compulab and 160 Mo for specific applications).
> 
> At the boot, there's a scanning of the MTD1 (4096 blocks) corresponding 
> to the NAND Flash.
> This scanning takes 1mn20s. The full boot time, from a reset to the 
> login prompt, takes 4mn.

Are you sure you enable "Summary support"?
What's your kernel version? Newer JFFS2 is quicker.

If you aready use latest JFFS2 and summary is enabled, then I am afraid
you do not have many options - may be improving HW?. 512 MiB is quite
large NAND for JFFS2.

Also, if you are curious, read one of the first chapters of my old JFFS3
document about JFFS2 scalability, it may be helpful to realize JFFS2
issues. 
http://www.linux-mtd.infradead.org/tech/JFFS3design.pdf

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: Reduce boot time with jffs2 and CM-X255

[Ricard Wanderlof]

> On Wed, 20 Dec 2006, Artem Bityutskiy wrote:
>
> Are you sure you enable "Summary support"?

At least in the 2.6.18 kernels, summary support is marked as EXPERIMENTAL. 
Is it stable enough to be used for production? (I don't know, just 
curious).

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Re: Reduce boot time with jffs2 and CM-X255

[Artem Bityutskiy]

On Wed, 2006-12-20 at 10:06 +0100, Ricard Wanderlof wrote:
> At least in the 2.6.18 kernels, summary support is marked as EXPERIMENTAL. 
> Is it stable enough to be used for production? (I don't know, just 
> curious).

Well, we heavily utilize it, and I know some serious projects like OLPC
where summary is utilized. So I would say it is stable enough.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: Reduce boot time with jffs2 and CM-X255

[Ricard Wanderlof]

On Wed, 20 Dec 2006, Michel LECONTE wrote:

> I use a CM-X255 with a NAND Flash of 512 Mo
> where roughly 250 Mo are used (90 Mo for the native distribution
> provided by Compulab and 160 Mo for specific applications).
>
> At the boot, there's a scanning of the MTD1 (4096 blocks) corresponding
> to the NAND Flash.
> This scanning takes 1mn20s. The full boot time, from a reset to the
> login prompt, takes 4mn.
>
> I hope that these precisions can be useful.

I don't know if this helps, but I have noted that when mounting a flash 
partition which contains lots of erased blocks/sectors, that jffs2 after 
the mount has completed in the background (re-)erases the blocks and 
writes cleanmarkers to them (the logic of this is clearly explained in the 
JFFS2 documentation on the mtd home page). For NOR flash, this can be 
alleviated easily by instructing mkfs.jffs2 to add cleanmarkers to unused 
parts of the image. For NAND flash, the cleanmarkers are stored in the 
out-of-band (OOB) area, which is normally not part of an image; 
consequently, it is easier to leave it up to jffs2 on the target system to 
erase and write cleanmarkers, which takes time, or at least takes up 
system resources, causing other processes to run slower. Admittedly, NAND 
is faster than NOR, but then you've got quite a lot of empty flash too 
(250 MB).

I don't know what the solution is - one idea is that a program like 
nandwrite could be instructed to write cleanmarkers to the OOB of unused 
parts of a partition. Currently there is no support for this but it could 
be added.

Hm, sidetracking here a bit, I'm thinking a general erase + write image 
utility for NAND flash would be useful, given that bad block management 
gets a bit hairy when you write to NAND and the write fails - should the 
block be re-erased (not really part of a nand writing tool's job) and 
retried, or just marked as bad (because most likely the block had recently 
been erased by an erasing tool)? Having erase+write in the same tool would 
make it easier for the tool to manage this, and it could also write jffs2 
cleanmarkers to the oob as part of the whole procedure.

Except for testing, most of the flash writing I come across is writing a 
complete image (usually jffs2, but also boot images) to a flash partition.

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Re: Reduce boot time with jffs2 and CM-X255

[Artem Bityutskiy]

On Wed, 2006-12-20 at 10:17 +0100, Ricard Wanderlof wrote:
> Admittedly, NAND 
> is faster than NOR, but then you've got quite a lot of empty flash too 
> (250 MB).

Just do not include empty eraseblocks to the image.

> I don't know what the solution is - one idea is that a program like 
> nandwrite could be instructed to write cleanmarkers to the OOB of unused 
> parts of a partition. Currently there is no support for this but it could 
> be added.

nandwrite -o ?

> 
> Hm, sidetracking here a bit, I'm thinking a general erase + write image 
> utility for NAND flash would be useful, given that bad block management 
> gets a bit hairy when you write to NAND and the write fails - should the 
> block be re-erased (not really part of a nand writing tool's job) and 
> retried, or just marked as bad (because most likely the block had recently 
> been erased by an erasing tool)? Having erase+write in the same tool would 
> make it easier for the tool to manage this, and it could also write jffs2 
> cleanmarkers to the oob as part of the whole procedure.

I would recommend to improve/re-work/upgrade nandwrite instead of a new
tool.

-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)

Re: Reduce boot time with jffs2 and CM-X255

[Ricard Wanderlof]

On Wed, 20 Dec 2006, Artem Bityutskiy wrote:

>> I don't know what the solution is - one idea is that a program like
>> nandwrite could be instructed to write cleanmarkers to the OOB of unused
>> parts of a partition. Currently there is no support for this but it could
>> be added.
>
> nandwrite -o ?

Yes, but that assumes the image contains the cleanmarkers. Can mkfs.jffs2 
create images with cleanmarkers in the oob? And wouldn't that conflict 
with mtd ecc usage, i.e. doesn't ecc information then also have to be in 
the image?

>>
>> Hm, sidetracking here a bit, I'm thinking a general erase + write image
>> utility for NAND flash would be useful, given that bad block management
>> ...
> I would recommend to improve/re-work/upgrade nandwrite instead of a new
> tool.

Yes I think that's probably the best route. I've been thinking about this 
for some time, but haven't really come to a conclusion about exactly what 
to include in such an upgrade. (I know I've posted some ideas earlier on 
the list; thanks for the responses btw).

/Ricard
--
Ricard Wolf Wanderlöf                           ricardw(at)axis.com
Axis Communications AB, Lund, Sweden            www.axis.com
Phone +46 46 272 2016                           Fax +46 46 13 61 30

Re: Reduce boot time with jffs2 and CM-X255

[Vitaly Wool]

Hello Michel,

Michel LECONTE wrote:
> I use a CM-X255 with a NAND Flash of 512 Mo
> where roughly 250 Mo are used (90 Mo for the native distribution
> provided by Compulab and 160 Mo for specific applications).
>   
I think that first of all this is a design problem. If you want smaller 
boot time, you need to figure out what exactly you need during the boot 
time and create minimalistic partitions. Anything else can be mounted 
later on.
Moreover, for the stuff that is effectively read-only I would recommend 
using read-only filesystem such as cramfs with a read-only translation 
layer, like this one: 
http://lists.infradead.org/pipermail/linux-mtd/2006-December/016973.html.

Well, that all doesn't mean you shouldn't use SUMMARY for your JFFS2 
filesystem. :)

Vitaly

Re: Reduce boot time with jffs2 and CM-X255

[Michel LECONTE]

First, I would like to thanks all of you for  your help and I want to 
specify that I'm newbie with jffs2 filesystem.

I have tried 2 methods to use the Flash :

1)

I didn't create a jffs2 image with mkfs.jffs2 and I didn't use sumtool.
I just copy my system on the flash mounted as specified in my first
post.

In this case, the boot time is about 4 minutes !!!


2)

I have created an jffs2 filesystem image :

./mkfs.jffs2 -r ../Distribution/ -o name.jffs2

and used sumtool :

./sumtool -i ../name.jffs2 -o name_1.jffs2

In the kernel, I enable "Summary support"

I tried to load this image in the flash with :

dd if=name_1.jffs2 of=/dev/mtdblock1

But I had an error message :

« dd: writing to `/dev/mtdblock1': Input/output error »

So I loaded this image with :

cp -r name_1.jffs2 /dev/mtdblock1

But when I boot the system I had :

« summary node crc error... »

With this second method, it doesn't work !!!


All I have read on the web deals about jffs2 filesystem image, so is it
necessary to create a filesystem image ?

What is the difference between filesystem image and a copy of the system ?

What I'm missing in the second method to explain my error ?


Thanks in advance for any suggestion or help.


Michel



Enrico Migliore a écrit :
> Hi Michel,
>
> could you be more specific?
> The boot time, in a production environment, is the time that elapses 
> from the board reset to the login prompt.
> How long is that time on your cm-x255?
>
> Enrico
>> Hi,
>>
>> I use a cm-x255 compulab card and I boot on the NAND flash with jffs2
>> filesystem.
>>
>> My problem is the boot is too long.
>>
>> My method to boot on the NAND flash is :
>>
>> 1) I boot on the cm-x225 via nfs.
>>
>> 2) I format the flash:
>>
>> flash_eraseall -j /dev/mtd1
>>
>> 3) I mount the flash :
>>
>> mount -t jffs2 /dev/mtdblock1 /mountpoint
>>
>> 4) I put the distribution of my system on the flash:
>>
>> cp -r /Distribution/* /mountpoint
>>
>> 5) I unmount the flash :
>>
>> umount /mountpoint
>>
>> 6) Finally, I boot on the cm-x255 board with the 2.6.18 kernel and
>> options are :
>>
>> - Boot options : root=/dev/mtdblock1 rootfstype=jffs2
>> ip=192.168.82.70:::255.255.255.0:arm:eth0
>>
>> - Miscellaneous filesystems : Journalling Flash File System v2 (JFFS2)
>> support
>>
>> JFFS2 debugging verbosity à 0
>>
>> JFFS2 write-buffering support
>>
>> JFFS2 summary support (EXPERIMENTAL)
>>
>>
>> I would like to know what I'm missing or what I have to do to decrease
>> boot time ?
>>
>>
>> Thanks for any suggestion or help.
>>
>> Michel
>>
>>
>> ______________________________________________________
>> Linux MTD discussion mailing list
>> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>>
>>   
>
>

-- 
*Michel LECONTE <mailto:michel.leconte@sacet.com>*
Tél : 02 99 57 15 81
Fax : 02 99 57 16 17

	
*SACET*
2 rue Maupertuis
Campus de Ker Lann
35170 - BRUZ - FRANCE
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