on small terminals, irqtop shows "(null)" at startup

Benno Schulenberg <[email protected]> Thu, 20 Mar 2025 10:57:50 +0100

Newsgroups	org.kernel.vger.util-linux
Message-ID	<[email protected]>

To reproduce, run `xterm -geometry 80x12 &`, and in that xterm
run `irqtop`.  See that the table of IRQs is empty at first,
apart from the string "(null)" -- like this:

    IRQ   TOTAL   DELTA NAME
(null)

After three seconds a list of IRQs appears.

Now open the window's menu (probably with Alt+Space) and choose
Resize.  Then press the right arrow key in a steady rhythm of
twice per second.  See that "(null)" gets shown almost constantly
at the start of the table.

Then reverse direction: keep pressing <Left> twice per second.
The "(null)" does not appear any more.  Then reverse direction
again: pressing <Right> twice per second.  The "(null)" will be
shown again as soon as you've reached a width you hadn't reached
before.

I can reproduce this on three similar 64-bit machines, but not
on an old 32-bit machine.


When using -S or -t2222 (which reduce the number of shown IRQs),
then the table appears right away.  Other options have no effect.

Commenting out the call of scols_table_enable_maxout(table, 1)
allowed the table to appear straightaway on my default terminal,
which made it seem that something is going wrong in libsmartcols.

So I did an `export LIBSMARTCOLS_DEBUG=all` in the shell, but
irqtop produced zero debugging output.  Only after adding a call
to scols_init_debug(0) in the main{} of irqtop, did it start
producing debugging output.  But it is verbose, and I don't know
what I'm looking for, so I've attached the result of:

    ./irqtop -c disable  2>TRAIL

on an `xterm -geometry 80x12`, where I've pressed q as soon as
the table did appear after three full seconds.


Benno

TRAIL.gz (application/gzip, 6.2 KB) - not displayed

OpenPGP_signature.asc (application/pgp-signature, 840 B)