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Re: SSD's and many edits of a single file




Gene Heskett wrote:
> On Monday 09 April 2018 06:18:18 songbird wrote:
>> Gene Heskett wrote:
>> > Greetings folks;
>> >
>> > Updodate Wheezy, realtime kernel because machine is running
>> > linuxcnc.
>> >
>> > Editor is geany and file is left open in the editor, and reloaded
>> > into linuxcnc as changes are made to the file, and saved but not
>> > closed.
>> >
>> > And eventually the updates made to the file are not actually saved,
>> > geany does not report an error and does say success by changing the
>> > filename font from red which tells me its been modified, back to
>> > black in the window top border, but does not actually update the
>> > file on the disk, and the only fix seems to be a reboot.
>> >
>> > Is this a known fault with some SSD's? Or???
>>
>>   i'm not familiar with geany or linuxcnc...  any options
>> in geany for save interval?
>
> I think 2 minutes.

  seems that isn't working, either a bug or you
have more than one copy of the same file open and
one hasn't changed and the other has?  or something
like that...


>>   what kind of file system? 
>
> ext4 w/journaling on.

  ok, so somewhat sane fs.  except you are using some
different hardware and perhaps that implementation
doesn't include all the fs options you think it may.
could be perhaps even ignoring some so...  ugh...
hard to debug.


>>   what are the mount options 
>
> defaults
>
>> in fstab?
> UUID=54273d27-b48f-4a73-9b4d-d3cd13c6ba79 /             ext4 
> errors=remount-ro 0        1
>
>>type of SSD?
> kernel: [    3.648318] scsi 0:0:0:0: Direct-Access     ATA      SPCC 
> Solid State V3.7 PQ: 0 ANSI: 5
>
> Cheap on sale special from newegg. Lots quicker than spinning rust. 
> Currently 28% used ack df.

  yes, i'm on SSD finally too, love it so far.  by
the time i need to add more i should be able to get
a few TB for the same price of this one.


> Thanks songbird.

  curious though why no vi/vim.  :)


>>   a sync once in a while like other poster recommended
>> may be a help as it would also clear out any waiting io
>> but i'm not sure how much that may interfere with the
>> realtime aspects if you have some large chunks waiting.
>>
> I can only guess.  These files are generally not long, 100 lines or so if 
> I write it but if generated by a code generator, which has no knowledge 
> of the looping abilities of linuxcnc's RS-274-D translator, could make a 
> 40 meg file out of what should be less than 100 properly constructed 
> lines of gcode.

  no of course not, you'd not want to see flattened out 
loops like that!  :)

  for that small of files you are editing, a sync should
mean nothing to the system.  the other issue though is
how the system deals with cached io pages and that was
all i was concerned about if there was something else
going on that would have large io blocks waiting to get
written to disk.  doesn't sound like it to me.


>>   i've used ionice for some things to make sure they
>> don't interfere on an older system with limited
>> capacity.
>
> The heart of linuxcnc runs on one core of a multicore cpu, and something 
> like ionice would probably get locked out of that playpen and have no 
> effect. Any effect would probably encourage it to wreck an otherwise 
> purty part. It, LinuxCNC, supplies the motor signals to drive the 
> machine to sub-micron accuracy, but to do that it has to be able to 
> slice time into nanoseconds.

  sound like fun, but i'd be a bit worried to have
a machine that large driven by a relatively unshielded
pc of any kind.

  do they even have ECC memory in them?  eek!
shielded from cosmic rays?


>> my current machine is a screamer in comparison 
>> so i've not had to do that.
>
> Most of this stuff isn't the latest and greatest.  Old Dell's, or Atom 
> powered shoeboxes even. What matters is how steady a heartbeat it can 
> maintain when a beat of the heart might be needed every 25 nanoseconds, 
> and the atoms are the fastest kid in town for that. The biggest machine 
> is a 1500 lb lathe, and its being run by an r-pi-3b using mesa 
> interfaceing cards. Might be the only one on the planet.


> Thanks songbird.

  y.w. it does all sound like fun, but a bit too high
on the risk scale for me.  where something wrong might
involve spinning metal, i'd want to be a long ways away.
had someone behind me get hit by an exploding wood bowl
once in jr. high shop class.  not a fun time...


  songbird