Re: dar became very slow (and process in D state?)

Il giorno gio, 16/01/2020 alle 13.20 +0100, Denis Corbin ha scritto:
> On 16/01/2020 09:54, Andrea Vai wrote:
> > Il giorno gio, 30/05/2019 alle 15.22 +0200, Andrea Vai ha scritto:
> 
> [...]
> 
> > For anyone interested, the full story is available at two threads
> > in the kernel mailing lists (starting at [1], and then [2]).
> 
> OK, good to know and thanks a lot for this detailed feedback!
Thanks to you Denis, and thank you Aaron for the comment :-)

> 
> > 
> > At the time of writing, I have workarounded the problem by using
> > an ssd drive instead of the "low quality" pendrive. In fact, it
> > seems that ssd drives are not affected by the problem (details are
> > in the kernel discussion threads linked below).
> > 
> > I hope all of this could help anyone with the same problem in the 
> > future.
> > 
> > On the dar side, there's another detail I would like to further 
> > investigate: I used to test the problem by running a "cp" command 
> > which clearly shows a difference in time with the old kernel vs.
> > new kernel. We found a way to workaround the problem by removing
> > the destination file before the begin of the file copy, but this 
> > workaround does not work if I use dar instead of cp: if I remove
> > the old archive before starting the new dar command, the operation
> > is stil "slow". Could anyone (Denis?) explain this behavior or say
> > whether it makes sense in the current scenario?
> 
> difficult to know for now, but I suspect the difference comes from
> the
> fact cp performs a sequential reading while dar by default reads the
> catalog at the end of the archive then skip back near the beginning
> of
> the archive then from time to time skips over the sequential marks
> that are used only when reading an archive in sequence.
> 
> To confirm this hypothesis, you would retry testing the same archive
> with the --sequential-read option.

I have just tried and didn't make any difference, but I am wondering
whether I am not understanding something. My problem appears while
writing a new archive, so does --sequential-read option matter as well
in that case?

the command I run is

# SECONDS=0; mount UUID=ae7ac0ca-d0bc-46c8-81f1-d2b67e1f95f3 /mnt/pendrive && rm -f /mnt/pendrive/aero.1.dar && dar -c /mnt/pendrive/aero -R /home/andrea/Musica/MP3/Aerosmith && umount /mnt/pendrive; echo "Ci ho messo: $SECONDS secondi."

which, as far as I know, doesn't involve reading a catalog, does it?

Thanks, and bye
Andrea