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Linux Kernel 4.9 and a (not so) happy Jornada 720

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munchausen Page Icon Posted 2021-01-03 1:41 PM
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Just saw about this awesome news, well done Stefan! Going to give this a go on my J720.

BTW I think mounting the rootfs on a CF as ext4 is not such a good idea, you will waste CPU cycles with journaling but a bigger problem is it isn't good for the limited write cycles on a CF card. ext2 should be OK I think, I will try it. Update: works fine, just gives a warning at boot.

Edited by munchausen 2021-01-03 2:01 PM
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joval Page Icon Posted 2021-01-04 2:47 AM
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munchausen - 2021-01-03 5:41 AM

Just saw about this awesome news, well done Stefan! Going to give this a go on my J720.

BTW I think mounting the rootfs on a CF as ext4 is not such a good idea, you will waste CPU cycles with journaling but a bigger problem is it isn't good for the limited write cycles on a CF card. ext2 should be OK I think, I will try it. Update: works fine, just gives a warning at boot.


I have found that CF cards are not really required...an SD card placed in a cf adapter works very well. Further partition one can be FAT 32 and at least 15 GB (haven't tried anything larger)...so your J720 can access a winCE hp backup file kept there to easily "dual boot" back and restore to your prior WinCE os/session. Would less journaling cycles speed up rendering any? I guess I will have to compare the two...ext4 vs ext2.

and I agree...Stefan has done an amazing job!

Edited by joval 2021-01-04 2:48 AM
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joval Page Icon Posted 2021-01-04 3:02 AM
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ntware - 2020-10-01 4:56 PM

Well, I guess that my guide also is not 100%. After a bit of testing I realized that it was missing one step. Even though the SSID information is stored in the card somewhere, I believe that when Linux reinitializes the card, it stays in limbo mode until you tell it to connect to the SSID again. So here are the full steps:

1. Configure the card on Windows CE as usual. Use the Aironet app to setup SSID information and make sure the connection works (open something on Pocket IE).

2. Boot into Linux and login as root.

3. To power up the card:
ip link set dev wifi0 up  
ip link set dev eth0 up
(apparently this card needs to be enumerated with both wifi0 and eth0). Once you run those commands, the LEDs on the card will start flashing and it will automatically connect to the SSID configured previously on Windows CE. 4. Connect to your SSID. I issued this command for both interfaces wifi0 and eth0. Not sure if it only needs to go to one of them:
iwconfig wifi0 essid "Your_SSID_without_quotes" mode Managed 
iwconfig eth0 essid "Your_SSID_without_quotes" mode Managed
5. Obtain an IP address from DHCP:
dhclient -v eth0
6. Or alternatively, if you want to set the card with static IP:
ifconfig eth0 "Your_fixed_IP_without_quotes" netmask 255.255.255.0 up 
route add default gw "Your_gateway_IP_without_quotes"


That's it!


ntware:

I can't imagine how you figured this all out especially the eth0 requirements...but IT WORKS great on WEP for ssh/x11 into RasPi! It only seems a little slower than using a wired ethernet NE 2000 compatible connection.

I haven't taken on the wpa_supplicant wifi option yet...that's coming next. But it is very nice to have the J720 completely free of any ethernet ribbon cable/tether and still fairly snappy rendering web pages (haven't tried youtube videos yet...). Thanks again for all your many efforts...ntware...and all the rest of you!
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munchausen Page Icon Posted 2021-01-04 10:56 AM
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joval - 2021-01-04 2:47 AM
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munchausen - 2021-01-03 5:41 AM
BTW I think mounting the rootfs on a CF as ext4 is not such a good idea, you will waste CPU cycles with journaling but a bigger problem is it isn't good for the limited write cycles on a CF card. ext2 should be OK I think, I will try it. Update: works fine, just gives a warning at boot.


I have found that CF cards are not really required...an SD card placed in a cf adapter works very well. Further partition one can be FAT 32 and at least 15 GB (haven't tried anything larger)...so your J720 can access a winCE hp backup file kept there to easily "dual boot" back and restore to your prior WinCE os/session. Would less journaling cycles speed up rendering any? I guess I will have to compare the two...ext4 vs ext2.


By default journaling adds information to the journal every time you access a file - even if you're just reading it and not making any changes! The effect is that the jornada CPU has to spend time doing these writes and computing what to put in the journal when it could be doing real work, the PCMCIA(/CF) bus has to do some extra writes which takes up time and bus bandwidth when they could be doing actually necessary disc IO, and the flash card (compact flash, SD card, it doesn't matter) is getting written to all the time for no real reason, which will eventually kill it. The extra writes are a significant overhead: A 2018 paper [1] says that with journaling ext4 does 2.7 times more writes than without, which will slow the system down and burn out flash faster, and this does not include time spent reading the journal or any extra processing for the CPU that is also bogging down the system. Perhaps ext4 without journaling is a better option than ext2 though.

The swappiness should also be turned right down for the same reason; using the swap file on flash will kill it in the end (and is also slow), so the swappiness should be set to tell the kernel to use it only as a last resort. Ideally the swap would be on another card completely, but that isn't an option if you want a network card too.

[1] https://csyhua.github.io/csyhua/hua-tc2018-journaling.pdf
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_dev-null Page Icon Posted 2021-01-04 2:44 PM
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Interesting infos about the file systems!
Would be interesting to do some sort of benchmark.

Regarding swap, I dont worry about the CF card, because there should be enough writy cycles to outlive the Jornada. Remember to have enough free space on the card. Then the wear leveling mechanism can do its magic.
I use several CF/SD cards in systems that have done a lot of write cycles and havent had a single failure in all these years.
But it is always good to reduce swapping, because it is slow. On the Jornada with only 32 or 64 and even with 128MB ram this is not an easy task. If you reduce swapping too much, the OOM killer runs very often.

Stefan
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munchausen Page Icon Posted 2021-01-04 3:47 PM
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I have killed a CF once, I still have it (Kingston, 16GB). I did it by installing windows 98 on it inside a vaio C1. I think 98 just thrashed the disk until it died. It was new when installed as well! But in any case, I think the performance overhead of a journal is a bad idea for a jornada.
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joval Page Icon Posted 2021-01-05 4:06 AM
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munchausen - 2021-01-04 7:47 AM

But in any case, I think the performance overhead of a journal is a bad idea for a jornada.


Right you are...using ext2 format does speed up response...and the root delay=5 isn't necessary on boot. How well things will go if system crashes unknown given no jornalling with ext2...but Munchausen (you can take another dose of the strong stuff...given the meaning of your name)...so far seems like a great suggestion just from the speed gain!!!!

I'm using an Aironet 340 wifi card via a wifi extender set to wep on one side and wpa2 on the internet side. It is working great...almost no delay writing this post letter by letter. The J720 completely untethered via wifi to RasPi. It's fast for 200MHz cpu.(getting a little help from my friend the RasPi).

Gonna checkout youtube now. Thanks again...you guys are super IMHO!!
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ArchiMark Page Icon Posted 2021-01-13 11:40 PM
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_dev-null - 2020-12-08 9:54 AM

Ok, it seems that we can't use iwconfig with this card, tried it and it also doesnt work for me.
A post from another forum:

"It sounds like either your kernel or the driver for the wireless interface will only support the newer cfg80211 configuration interface used by the iw tool, not the older wireless-extensions interface used by iwconfig."

If I find time, I will figure out a solution. But before I have to recompile CRDA to set the correct country code ...

Stefan



Hi Stefan,

Any luck with the Ambicom card and WPA ?

Thanks,

Mark
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_dev-null Page Icon Posted 2021-01-14 6:01 PM
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No sir. I have to say I hate this card... Nothing works as expected.

Let you know if I make some progress...

Stefan
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ArchiMark Page Icon Posted 2021-01-14 6:04 PM
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Thanks for letting me know...

Will think positive for making progress....

Mark
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can't remember Page Icon Posted 2021-01-19 11:51 PM
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can't remember - 2020-11-20 12:08 AM

@_dev-null: the exact error message is "sudo: error while loading shared libraries: /usr/lib/sudo/libsudo_util.so.0: file too short"


I finally got this working, turns out my file system somehow got damaged, I can now run sudo and other commands that were failing and start X (but touchscreen is not properly calibrated and I don't know how to calibrate it on Devuan).
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X_Files.CZ Page Icon Posted 2021-02-16 6:37 PM
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Hi all,
is the "http://www.sp-net.at/" down? Or is just unreachable from central Europe? (Czech Republic)
I found a new motherboard for my J720 so I want to try this miracle.
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ArchiMark Page Icon Posted 2021-02-16 7:26 PM
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Hi X_Files.CZ,

Just tried site and it didn't load for me either, from here in USA.

Welcome to HPCFactor and Debian on J720!

Mark

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_dev-null Page Icon Posted 2021-02-17 7:49 AM
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Hi!
Sorry, the Raid controller in of the server died again. The replacement part took a while to arrive. I replace it in the next couple of minutes!


Regards
Stefan

Edited by _dev-null 2021-02-17 7:51 AM
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_dev-null Page Icon Posted 2021-02-17 8:22 AM
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Back online again!
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