Fedora xen - Aug 2007 - ANNOUNCE: Virt-top - a top-like utility for displaying virtualization stats

I''m pleased to announce the first release of virt-top, which is a 
top-like utility for displaying virtualization stats.

It aims to look and feel very much like regular ''top'', so as
to be as
familiar as possible for systems administrators.  You can also use it as 
a pleasant replacement for xentop.

It uses libvirt, so can display stats across a variety of different 
hypervisors and virtualization systems (not just Xen, although that is 
where the testing has gone so far).

   http://et.redhat.com/~rjones/virt-top/

The license is a combination of LGPL (for the library) and GPL (for the 
virt-top program).

Current status
--------------

You can view domains and use familiar keys like
''P''/''M''/... to sort by
processor/memory/..., and ''d''/''s'' to set the
delay between updates.
Also some common top command-line options are implemented.  The man page 
is here: http://et.redhat.com/~rjones/virt-top/virt-top.txt

There are a variety of source and binary RPMs available for Fedora 
users.  I don''t yet have a working Debian/Ubuntu package, but will have
a go at making one tomorrow.

The next thing I''ll be working on is showing virtual and physical CPU 
usage of guests.  After that I''m hoping to discuss extensions to
libvirt
to make other interesting statistics available to virt-top, in 
particular disk and network I/O stats.

There are a few data collection artifacts which need to be investigated. 
  In particular, %CPU sometimes goes over 100%.  Obviously accurate data 
collection is an important goal for this tool.

Memory usage is good: typical ''RES'' (in regular top) for
virt-top is
just under 2.5 MB, and I''ve had it running for hours at a time without 
memory usage increasing, which seems to indicate that there aren''t any 
major memory leaks.

Development
-----------

The program is currently very small: exactly 500 lines of code!

If you want to dive in and send me patches they are most welcome, but 
remember that I''m trying to make this utility act as much like
''top'' as
possible, so if ''top'' does it in a particular way, then
I''d prefer
virt-top to do the same thing.  (May not apply to obscure top 
functionality, if top does something silly).

If you''re a systems administrator, not a programmer, and you''d
like
virt-top to have some particular feature, then please let me know, and I 
will be happy to review it and code it for you.

Rich.

-- 
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom.  Registered in
England and Wales under Company Registration No. 03798903

On Mon, Aug 06, 2007 at 10:15:48PM +0100, Richard W.M. Jones
wrote:
> There are a few data collection artifacts which need to be investigated. 
>  In particular, %CPU sometimes goes over 100%.  Obviously accurate data 
> collection is an important goal for this tool.
AFAICT it is impossible to stop it going over 100%  - we have same issue 
in  virt-manager when calculating CPU usage. To caculate the % usage you 
are looking at the differential between CPU time from two calls to 
virDomainGetInfo vs the time period between two gettimeofday() calls.
If the time delta between your gettimeofday() calls does not exactly 
match the time delta between your virDomainGetInfo() calls, and the 
domain you''re measuring is very active then you can end up calcuating
> 100% occassionally. Not by much - typically < 1% over, but I
don''t
really see any way around it.

Regards,
Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
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On Mon, 6 Aug 2007 22:31:24 +0100
"Daniel P. Berrange" <berrange@redhat.com> wrote:
> If the time delta between your gettimeofday() calls does not exactly 
> match the time delta between your virDomainGetInfo() calls, and the 
> domain you''re measuring is very active then you can end up
calcuating
> > 100% occassionally. Not by much - typically < 1% over, but I
don''t
> really see any way around it.
Shucks, it is easy to work around:

   if (percentcpu > 100) percentcpu = 100;

:-).

On Mon, Aug 06, 2007 at 07:18:35PM -0400, Tom Horsley
wrote:
> On Mon, 6 Aug 2007 22:31:24 +0100
> "Daniel P. Berrange" <berrange@redhat.com> wrote:
> 
> > If the time delta between your gettimeofday() calls does not exactly 
> > match the time delta between your virDomainGetInfo() calls, and the 
> > domain you''re measuring is very active then you can end up
calcuating
> > > 100% occassionally. Not by much - typically < 1% over, but I
don''t
> > really see any way around it.
> 
> Shucks, it is easy to work around:
> 
>    if (percentcpu > 100) percentcpu = 100;
When I said "i don''t see any way around it" I meant a way
which would be
calculating correct/accurate figures. Clamping to 100% is just pretending 
the problem doesn''t exist - though it is the hack I am already using 
in
virt-manager. 

Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=|

There is a significantly updated version of virt-top now available.  On 
systems which support it, you can show the mapping of domains to 
physical CPUs and the amount of each physical CPU being used.

Screenshots: http://et.redhat.com/~rjones/virt-top/screenshots.html

There are also binaries available to download for i386 and x86-64.  (The 
binaries are just self-contained Linux executables, no extra files or 
dependencies are needed, except for libvirt.so).

Downloads: http://et.redhat.com/~rjones/virt-top/download.html

If you are a systems administrator, what do you think could be improved 
about virt-top?  Try it out and let me have your suggestions ...

Rich.

-- 
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom.  Registered in
England and Wales under Company Registration No. 03798903

Andy Burns wrote:
> On 09/08/07, Richard W.M. Jones <rjones@redhat.com> wrote:
> 
>> There is a significantly updated version of virt-top now available.  On
>> systems which support it, you can show the mapping of domains to
>> physical CPUs and the amount of each physical CPU being used.
> 
> I downloaded the binary 64bit version and ran it on a fedora 7 xen
> host without any problems, the host is a dual-core xeon andnoticed
> the CPU% reporting works differently compared to xentop, I assume this
> is deliberate?
Thanks for trying this!  I was on holiday last week, hence the late reply.
> virt-top seems to report each domain''s usage as a percentage of
all
> the sum of all CPUs, where xentop seems to report the percentages in
> terms of a single CPU.
> 
> e.g. on xentop may show dom0 taking 102% and my domU taking 24%, while
> virt-top will shows this as 51% and 12% respectively, which seems more
> logical.
Yes, this is deliberate.  We wanted to make it work like virt-manager 
and plain top.  Notice that xentop is the exception in this regard.

Rich.

PS: I will be making available proper binaries for RHEL, Fedora, CentOS 
and Debian, i386 & x86-64, this week.

-- 
Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/
Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod
Street, Windsor, Berkshire, SL4 1TE, United Kingdom.  Registered in
England and Wales under Company Registration No. 03798903