xu4 Linux Performance Note & Personal Boat Note

A couple of unrelated things, one tech and one personal.

Linux Devuan XU4 Performance Note

This is a bit in the weeds, but I’d copied some system directories onto disk file systems.

Hardware: Odroid XU4 with 2 GB memory and 8 cores (32 bit v7 ARM).
Toshiba 1 TB USB hard disk (2.0 USB IIRC) somewhat older.

Software: Linux – Devuan 3.0 Beowulf.

Present “disk” layout:

root@XU4uDevuan3:/# df
Filesystem     1K-blocks    Used Available Use% Mounted on
udev              949528       0    949528   0% /dev
tmpfs             204124    6308    197816   4% /run
/dev/mmcblk1p2  12192904 7439428   4111020  65% /
tmpfs               5120       4      5116   1% /run/lock
tmpfs             827660  213980    613680  26% /dev/shm
/dev/mmcblk1p1    130798   16742    114056  13% /boot
tmpfs            2097152   12896   2084256   1% /tmp
/dev/sda6        1998672    3152   1890664   1% /T1/tmp
/dev/sda9        6127168 3468984   2343612  60% /T1/usr
/dev/sda10       6127168  690196   5122400  12% /lib
/dev/sda11       6127168 2774412   3038184  48% /var
/dev/sda7        5095040 3591356   1252052  75% /home/ems
none             1020608       0   1020608   0% /run/user/1600

Note in particular the file system on /dev/sda9 /T1/usr. This is a copy of /usr that lives on the root partition /dev/mmcblk1p2 on the uSD card.

Here’s the gparted report on that disk:

Devuan XU4 USB disk layout

Devuan XU4 USB disk layout

Note, too, that I’ve movted /lib and /var onto the hard disk (and there is a /dev/sda6 /T1/tmp where I tried using the hard disk for /tmp instead of using a memory based tmpfs…)

So looking at that image, you can see that most of the disk is a large file system for storing things rarely used (/dev/sda4), then a couple of swap partitions, and then the usr lib var and tmp partitions, a bit of unused space, and my home directory on this system.

The “bottom line” is that putting it all on disk was SLOWER than this particular split. My suspicion is that it is due to contention between the /usr /var /lib and /home/ems partitions on the disk causing minor head seeks. While all of these partitions are close to each other on the disk, they are still not the same tracks.

Those swap partitions are largely for the Aw Shit case, as there is 2 GB of “memory compressed zram swap” that gets used first. So essentially the head will mostly hover over the /var and /lib partitions.

Having /usr left on the uSD card was significantly faster, observable in human time even.

I suspect that this split lets all the /usr stuff come off the uSD card fast and without regard to rotation or location, while the /var and /lib stuff has a head over it and it is loading into other buffers.


It is much faster than all on disk, and also faster than all on uSD card.

Other side note: I copied the /usr files with “cp -r” and that caused a problem with su not keeping SUID permissions and another program at login complaining. OK, for decades I’ve used “tar cvf – .” piped into “tar xf -” to good effect. Guess “cp -r” isn’t quite ready to do perfect copies and I’ll go back to the “Old School” way.

Was that “an issue”? I don’t think it caused sloth, but didn’t bother to test that idea.

Personal Note

The Boat has an 11 foot (something) inches beam (or near that) AND escrow has closed. I’m now 1/2 owner with Florida Friend of a boat in Florida. “Watch this space” as about end of February into March I expect to be posting some Stuff from said boat.

We’ll be sailing a bay, and when comfortable with the boat, out into Blue Water Atlantic for a day or two.

The Adventure Begins!

Now I’ve really got to get my ass to Florida ;-)

Subscribe to feed

About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
This entry was posted in Human Interest, Tech Bits. Bookmark the permalink.

21 Responses to xu4 Linux Performance Note & Personal Boat Note

  1. Logau says:

    ¡Boat: C o n g r a t u l a t i o n, Captain Smith!

  2. E.M.Smith says:

    Thanks! It’s been a while since I was sailing so we’ll see how fast it comes back ;-)

    Looking forward to fishing off the aft swim deck ;-)

  3. If you don’t already know of it, check out Lee of Christian Island” – Gordon Lightfoot.

  4. H.R. says:

    @E.M. – At one of my fishing docks on the Intercoastal, there’s a marina off to the side.

    A couple of times, I’ve watched this guy in a – ohh, just guessing and going from memory – about a 30’+ single mast sailboat practicing all under sail. No motors for this guy. Mainsail, jib, and spinnaker.

    The times I saw him out, he’d go out and run upwind, downwind, and crosswind and it was clear he was trying to hit specific points and hold specific lines. Then he’d come into the marina to his dock, and when he had tied up, he’d cast off and do it all again.

    This was all by himself and all under sail. This guy was GOOD! I’m guessing he just might be one to enter solo sailing races of some sort.

    Anyhow, you and FF might try practicing some lone sailing – one of yuz jist sets & watches – because who knows when one of you will have a heart attack just as the engine decides to go on strike?

    Plus, there’s the fun and challenge of it all. You might consider playing around with that a bit after you get your sea legs.

  5. Ossqss says:

    And the name of the boat is?

    [Hopefully not Minnow! :-)]

  6. another ian says:

    RE Ossqss says:
    15 January 2022 at 8:46 pm
    And the name of the boat is?

    I’ve seen “404 Fish not found”

  7. E.M.Smith says:


    “Not To Be Disclosed”… as names are searchable and it will come with other names and addresses and such. Unofficially: “The Null”

    @Mobile Aviator:

    I’ll look for it!


    I’ve done most of that, except for rounding up into the dock on my 27 footer. I did round up to the dock on smaller sail boats (with no motor) and mostly remember how to do it. But with 4000 lbs of lead ballast I was “unwilling to risk dock repairs” ;-)

    This boat is bigger and heavier. FF is already taking sailing ASA classes, and those include rounding up to an anchor buoy in the bay. I’ll be willing to practice it there, too.

    FWIW, I did single hand my boat all the time for several years. Never had crew… I’m not used to the idea of 2 people sailing the boat at the same time ;-) FF is doing it as “crew”, but has already had one “stand the night watch” which is solo on overnight sails. So neither of us is going into this low on practice / skills.

    One thing I’ve not done is “Heave Too”

    There’s several other ways to “stop a sailboat” and I’ve mostly used some of them:

    So “heave too” is on my “to do” list.

    Also I’ve not used a Spinnaker. Just never felt the need. But this boat has one, so at some time or other will hoist it. I was good with just going “wing and wing” downwind with a big roller reefer jib and mainsail.

    So yeah, some stuff for me to learn, but I’m mostly interested in just handling the boat well, not doing fancy stuff. So I’ll round up to a halt under sail at a mooring buoy, but not in the confines of a dock where it’s about one boat length between boat asses … and you want to make a precise 90 degree turn. A single unexpected gust of wind and you can be buying some expensive toys… for someone else… So I’ll satisfy the hubris at the buoy and just enjoy the Diesel in port.

    Besides, you need to run it every so often to keep things dry, lubricated, and the battery topped up. Also fuel does not keep forever. While Diesel is good for several years, you don’t want it getting water on the bottom and growing a nice bit of algae clog in the fuel filter only to find out it won’t start when that freighter comes out of the fog right at you… Better to find that out at the dock when you try to exit under Diesel… and have not yet cast off.

  8. E.M.Smith says:

    Oh, and H.R.:

    Due to Florida Law saying the driver of the boat gets a DUI if drinking, one of us will often be single handing while the other one enjoys the beer… We’ll alternate days ;-)

  9. H.R. says:

    I sailed Lightning Class sailboats in H.S. Not one, but two of my buddies’ dads had them moored on a nearby reservoir. The club had its own marina and there were about 50 or 60 of these pretty much identical boats.

    The races were sailed with the ‘Captain’ and two crew members. I went sailing a few times fer funsies with one of my buddies (we’d take the girlfriends along), and I was fill in on the other buddy’s boat so ‘dad’ could practice. I never got to crew in a race. His dad was looking for someone with more meat on their bones for higher speed turns. You’d harness up and lay out horizontal. I was 135 lbs and I never met the guy I was subbing for, but I think he was more like 180 or 190 lbs.

    Here’s a good overview of the Lightning Class from the official source; pictures, rules, specs, etc.


  10. philjourdan says:

    Arrrggg Cap’n Smith, Ye be amazed at the gud Friends that come round to see ya now! Live well me hearty! And smooth sailing!

  11. E.M.Smith says:

    Lightning Class looks like fun!

    Personally, I get more fun out of a 15′ or so single handed than out of a big boat. Closer to the water and all ;-)

    Some of the most fun I’ve ever had was on a 14′ Hobie Cat (catamaran) on a lake in the summer. Going full tilt boogie and then doing a Pitch Pole (dig in a low side pontoon and the thing turns over upside down rapidly tossing you into the air forward…) was always exciting ;-)

    But not interested in a good Dunking in Florida Waters (what with gators and crocs and all…). Saw interesting video of about a 12-14′ salt water croc in a Florida marina fishing around the boats… so further from the water is better…

  12. Ossqss says:

    Maybe not eh same lightning discussion, but this is amazing stuff from the Volcano event.


    400,000 in a couple hours? Yikes!


  13. E.M.Smith says:


    I’m expecting a large flock of “New Friends” between having a guest room near Disney World and a boat on the coast…

    Once we’re settled in, I expect to announce “meets” where we can rendezvous at a nearby bar (so as to lose any undesirables / avoid mobs…) then relocate to boat or other venue. Basically putting a public address between posting and actual end point.

    Oh, and do realize that “Sudden Friends” are also know as “Working Crew” ;-) First rule of sailing.

    In short, while it’s been valuable to me to “Run A Blog” working on some of the bigger issues of the day (unfortunately, it looks like they are political driven frauds… both “Global Warming” and Chinese Wuhan Covid Vexxinations…), I expect that I’m ready to “retire from my retirement” after I’m in Florida. I don’t see where I can ever completely just stop. However, the clock is the master, and it’s likely time for someone else to step up to the plate on Big Issues. I think I need to do more postings about “Wine in the Caribbean” and “Fishing the inter-coastal” ;-) Spend less time up close and personal with computer guts and political intrigues.

    But, as usual, Fate Is My Master, and IFF it turns out that Pillousi and Bidetn et. al. continue their Soros Funded Assault On America, then I may just need to stay in the saddle a bit longer… At least a few days of the week… While I’d love nothing more than to walk away from anything political and concentrate on my Tan, Beer Drinking Skills, and Fishing Technique: Only will happen IFF I can do that with a clear feeling that America is not being abused by the GEBs.

    Do what you must, enjoy what you can.

  14. philjourdan says:

    @EM (err, Cap’n EM)

    Pillousi and Bidetn et. al. continue their Soros Funded Assault On America, then I may just need to stay in the saddle a bit longer

    It seems to me that someone else said something similar. Sadly we lost him last year, almost a year ago. You already know the answer to that unasked question. But your fan club will abide the slower postings due to being at sea.

    Might want to change your Blog name however. Cap’n EMS sounds good!!!

  15. E.M.Smith says:

    Well… a ship can not abide 2 Captains… and the FF is going to be the Liveaboard (aka “security” and “maintenance” ;-), so I think I can not take the title of Captain from him. I’m going to be ashore much more. So clearly there’s only one title appropriate to that role. As the person involved with funding and logistics and such, I think I’m only a lowly “Rear Admiral” so Admiral EMS ;-)

  16. H.R. says:

    @philjourdan re ‘boat friends’ – The only thing better than owning a boat is having a friend that owns a boat. 😁

    @Ossqss – that lightning strike gif was amazing. At first it seemed like a messy job of an attempt to show… something. After watching it a couple of times, I got my eyes adjusted to seeing the strikes and returns. Yikes! indeed.

  17. H.R. says:

    @E.M. – The Null Hullpothesis?

    Or you could just go old school with “Betty”.

  18. philjourdan says:

    @EM – let’s do not go down the “rear Admiral” path! That is not an image you want to evoke.

    Admiral EM is good. My neighbor (also with the same name as mine! But he is from Bangladesh, so we had a good laugh about it). Has a Motorboat, a canoe and a skiff. So I have come to call him “Admiral Halder”!

    Admiral EMS it is!

  19. E.M.Smith says:


    Yes, Admiral unadorned will be fine… ;-)


    Until further notice, the boat name is “Null”, OK?

  20. E.M.Smith says:

    Those lightning loops are amazing!

    If the explosion and ash fall don’t get you, it looks like the lighting will fry you…

Anything to say?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.