Re: Bad fs performance, IO freezes

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-10-29 11:49, cheater00 . wrote:
> Hi Austin,
> seek times are fine, but this literally freezes my computer for a
> split second. I've had to re-type this email twice because the freezes
> meant letters I typed would not arrive on the screen.
> USB disks are so common they should not be having issues.
That's debatable.  USB is commonly used because it's almost impossible 
to find a system that doesn't have it, not because it's reliable.  The 
original intent was for it to be used for stuff like mice and keyboards, 
so it was designed with low-latency and fair scheduling in mind, both of 
which really hurt performance of bulk data storage devices.
> I have 4.3.0-040300rc7-generic #201510260712 which is just three days old.
That should be perfectly recent enough, although FWIW, the official 
version of 4.3 should be out this Sunday.
>
> Please advise. Isn't it better to *not* use a vm to debug this?
That depends.  For something like this, it could go either way.  I just 
use a VM because that's what I always use, because it's nice not 
crashing your system when trying to debug a kernel panic.
> BTW, if we are talking about slow speed making things worse, I could
> try downgrading the cable to usb2.
> Is there a standard virtualbox VM that I could use?
In general, it's pretty easy to set something like Ubuntu up in 
VirtualBox, the install is essentially identical to regular hardware 
aside from the initial setup of the VM itself.  The documentation for 
VirtualBox is really good, if you've never used virtualization before, 
it's definitely worth reading.
> I'll download Gentoo in the meantime. I have never used it. I'm
> getting the "minimal installation cd" from 29th september.
> http://distfiles.gentoo.org/releases/x86/autobuilds/20150929/install-x86-minimal-20150929.iso
I meant by no means that you needed to use Gentoo, I only mentioned it 
because it's what I use (which in turn is because that's what I use on 
just about everything except stuff like the Raspberry Pi or the 
BeagleBoard).  If you just want to debug this and then be done with it, 
I would actually advise against using Gentoo, it takes a lot of effort 
to get a system up and running with it, and it's very involved to 
maintain compared to Ubuntu.  On the other hand though, if you are 
willing to learn to use it, it's one of the most highly customizable 
Linux distros out there, and can have noticeably better performance than 
more generic distros (FWIW, it's also one of the last big distros that 
doesn't force systemd on it's users by default).


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