Bug#675934: st - slow tape read/write rate

[Jonathan Nieder <jrnieder@gmail.com>]

Yury O. Tabolin wrote:
> 20.06.2012 07:22, Jonathan Nieder wrote:

>> For (i): could you try 2.6.37-2 and 2.6.38-rc6 from
>> snapshot.debian.org and let us know how it goes?
>
> The result of trying 2.6.37-2 is same as 3.2 early. Segfault
> disappeared. The read rate is about 10-13 MB/sec.

Drat, ok.  How about 2.6.36-1~experimental.1 or something near
2.6.33?

[...]
>> For (ii): if you get a change to try 3.4.y from experimental, that
>> would be very useful.
>
> With kernel 3.4.1-1 from exprimental nothing changed. No segfault.
> The rate is a some unstable, about 9-16 MB/sec.

Thanks much for checking.  Please report the speed regression upstream
to linux-scsi@vger.kernel.org, cc-ing Kai Mäkisara
<Kai.Makisara@kolumbus.fi> and either me or this bug log so we can
track it.  Be sure to mention:

 - steps to reproduce, expected result, actual result, and how the
   difference indicates a bug (should be simple enough)

 - which kernels you have tested and how each performed, roughly

 - full "dmesg" output from booting and testing on an affected kernel,
   as an attachment or link

 - a link to this bug log for background

If we're lucky, someone might have ideas for tests to try to pin down
what in particular got worse.  Or they might just ask you to bisect. :)

Thanks for making sure the st driver continues to work well, and sorry
I have no better ideas.

Hope that helps,
Jonathan