Re: Slow I/O on USB media

[Alan Stern <stern@rowland.harvard.edu>]

On Mon, 17 Jun 2019, Andrea Vai wrote:

> Il giorno lun, 17/06/2019 alle 12.14 -0400, Alan Stern ha scritto:
> > On Mon, 17 Jun 2019, Andrea Vai wrote:
> > 
> > > [...]
> > > 
> > > That happened ALL times, so I never encountered a kernel that made
> > me
> > > say "git bisect good".
> > 
> > Really?  That strongly suggests that the 4.20 kernel also should
> > have
> > been marked bad.  Did you really test it exactly the same way as all
> > the others?  That is, did you go through the entire procedure
> > starting
> > with "git checkout v4.20", then running the build script, then the
> > reboot and "uname -a", and then the test script?
> 
> well, honestly, no, because (sigh) I didn't know the "git checkout"
> command, sorry. I started with building 4.20 from the source
> downloaded with
> 
>  wget https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/snapshot/linux-4.20.tar.gz
> 
> , then said "git bisect good v4.20".
> 
> Is this different from "git checkout v4.20"? I hope it is, so we have
> found the mistake I have done.

In theory the results should be exactly the same.  But it doesn't hurt 
to check.

> > Compare the mainstream 4.20 kernel with the Fedora 4.20.13 kernel.  
> > Also, maybe compare the mainstream 4.20.13 with Fedora's 4.20.13.
> 
> Sorry, what do you mean here by "compare"? And what is the
> "mainstream"? If the mainstream is the one I got with wget, and if
> "compare" means "see if they behave differently", so I have already
> done it and they are both "good".

I was trying to point out that there may be a significant difference
between 4.20 and 4.20.13.  But if you say 4.20 behaves well, this 
doesn't matter.

At any rate, you are some commits you could try (beginning with "git 
checkout <commit>" and then running your scripts):

	c76cd634eb5b
	b1669432b355
	507413a5f88a
	a52fb43a5faa
	38fabca18fc4
	fc2fd5f0f1aa

These are all between 4.20 and 5.0-rc1.

Alan Stern