Re: [PATCH] xentop: Dynamically expand some columns

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Oct 03, 2014 at 10:00:30AM +0100, Ian Campbell wrote:
> On Thu, 2014-10-02 at 13:05 -0400, Konrad Rzeszutek Wilk wrote:
> > On Thu, Oct 02, 2014 at 10:25:41AM -0600, Charles Arnold wrote:
> > > >>> On 10/2/2014 at 10:10 AM, Andrew Cooper <andrew.cooper3@citrix.com> wrote: 
> > > > On 02/10/14 16:58, Charles Arnold wrote:
> > > >> Allow certain xentop columns to automatically expand as the amount
> > > >> of data reported gets larger.  The columns allowed to expand are:
> > > >>
> > > >> NETTX(k), NETRX(k), VBD_RD, VBD_WR, VBD_RSECT, VBD_WSECT
> > > >>
> > > >> Author: Markus Hauschild <Markus.Hauschild@rz.uni-regensburg.de>
> > > >> Signed-off-by: Charles Arnold <carnold@suse.com>
> > > > 
> > > > In principle, very nice.  (I have wanted to see about doing this for a
> > > > while now, but very far down the todo list)
> > > > 
> > > > How about the NAME field? 9 characters isn't enough for some people.
> > > 
> > > Sure, and any others that might need it.  But what to do about the '-f' flag
> > > which says show me the full VM name but the flag doesn't adjust the entire
> > > column.  By automatically showing the full name and adjusting the column
> > > appropriately it makes this flag pointless (which I'm ok with). 
> > 
> > Perhaps this functionality should be under that option?
> > 
> > I am a bit hesistant about this as there are some users of xentop that
> > use it for their monitoring. What I can't remember is if they use the
> > batched mode or not - and if they scan for specific strings (and length).
> > 
> > This would (I think?) throw a wrench in that?
> 
> IMHO people who are parsing the output of tools such as this ought to be
> prepared to deal with occasional changes in the precise content of the
> output across Xen releases.
> 
> If they aren't happy with that then they should file wishlist bugs (or
> better: patches) asking for an extensible/machine-readable format to be
> output upon request, or for libxenstat to be exposed and made API
> stable, or some other functionality which solves their need.
> 
> Otherwise we find ourselves in a position where useful patches like
> Charles' and similar patches which add genuinely useful output for human
> readers can never be accepted.

I dug up why -f was added, and this:

mit 422f39c72e1a9890636a770cb93de05b93f0e605
Author: Keir Fraser <keir.fraser@citrix.com>
Date:   Wed Dec 2 18:43:28 2009 +0000
 xentop: Allow full domain name display
    
    Add a '-f' option to xentop to allow the full domain name to be
    displayed. This is the original behavior which can cause the display
    to be unaligned. Customers have requested this because only the
    trailing characters of their domain names are unique and therefore
    cannot be distinguished when the display is limited to a 10 character
    width.
    
    Signed-off-by: Charles Arnold <carnold@novell.com>

OK, so this is all about 'aligment' of columns - and wanting to preserve
that without the usage '-f'.

Looking over your v2 patch it seems that it would keep that aligment in
check. That is if the aligment MUST change (one of the guests has a huge amount
of data), then ALL of the fields for ALL guests change their aligment?

If that is the case, then V2 is the proper way to go.