Re: [PATCH] tools/xentop: add option to display dom0 first

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, Feb 06, 2024 at 03:38:05PM +0100, zithro wrote:
> On 05 Feb 2024 18:27, Anthony PERARD wrote:
> > On Wed, Jan 31, 2024 at 06:51:34PM +0100, Cyril Rébert wrote:
> > > Add a command line option to xentop to be able to display dom0 first, on 
> > > top of the list.
> > > This is unconditional, so sorting domains with the S option will also 
> > > ignore dom0.
> > > 
> > > Signed-off-by: Cyril Rébert (zithro) <slack@xxxxxxxxx>
> > Your patch looks like a good idea
> 
> Thanks, I also have a "display dom id column" in the pipes, almost ready to
> send, but I found kind of a bug doing this (field_id/fields offsets off by
> one).
> Are there "most wanted functionnalities" concerning xentop, while I'm at it
> ? There's a TODO in xentop's folder.

That TODO file is 18 year old, and never been touch since. I don't know
how relevant it is. As for wanted features, I'm not aware of such list.

> Things I'd like to add, if possible, is domain management (pause/unpause,
> maybe shutdown/destroy), columns hiding and domains hiding.

I'm slightly worried about adding domain management, what if someone hit
the wrong key and kill a domain when they just wanted to do something
else, but I guess we can make domain management work more or less
safely. In any case, any feature is welcome.

> > but xentop segv without '-z' now, when there are guest running.
> 
> I failed at the strict minimum here, should have tested ... Sorry for
> wasting your time !

No worries, and your patch was reviewed so you didn't failed to the
strict minimum ;-).

> Bug spotted ("sort_start" incorrectly initialized), will post a v2.
> 
> > Revelant part of a backtrace:
> > #0  xenstat_domain_name (domain=0x121) at xenstat.c:344
> > 344         return domain->name;
> > #6  0x00006344dd283651 in top () at xentop.c:1209
> >          i = 2
> >          num_domains = 2
> >          sort_start = 1
> >          sort_count = <optimized out>
> >          dom0_index = <optimized out>
> > 1209                qsort((domains+sort_start), (num_domains-sort_count), 
> > sizeof(xenstat_domain *),
> > 1210                      (int(*)(const void *, const void 
> > *))compare_domains);
> 
> What soft did you use to get that output ? A debugger ?
> (It's a real question, I'm a noob).

I've used `gdb`, the GNU Debugger. There's plenty of tutorial on the
internet on the few commands that are useful to get started. And you can
run your program with gdb or run it on a coredump.

What I pasted, is a mixture of running the command `bt full`, and `list`
and `up`/`down` to get to the function I wanted to print a bit of the
source code.

Cheers,

-- 
Anthony PERARD