Re: [pve-devel] [PATCH pve-manager 2/3] Fix #5708: Add CPU raw counters

[Daniel Kral <d.kral@proxmox.com>]

On 9/17/24 07:50, Sascha Westermann via pve-devel wrote:
> Add a map containing raw values from /proc/stat and "uptime_ticks" which
> can be used in combination with cpuinfo.user_hz to calculate CPU usage
> from two samples. "uptime_ticks" is only defined at the top level, as
> /proc/stat is read once, so that core-specific raw values match this
> value.
> 
> Signed-off-by: Sascha Westermann <sascha.westermann@hl-services.de>
> ---
>  PVE/API2/Nodes.pm | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/PVE/API2/Nodes.pm b/PVE/API2/Nodes.pm
> index 9920e977..1943ec56 100644
> --- a/PVE/API2/Nodes.pm
> +++ b/PVE/API2/Nodes.pm
> @@ -5,6 +5,7 @@ use warnings;
>  
>  use Digest::MD5;
>  use Digest::SHA;
> +use IO::File;
>  use Filesys::Df;
>  use HTTP::Status qw(:constants);
>  use JSON;
> @@ -466,6 +467,37 @@ __PACKAGE__->register_method({

note: the same route also gets called when using the WebGUI and a set of 
the values that get returned are displayed on the "Node > Status" page. 
What I have seen, the added data size is very negligible.

>  	$res->{cpu} = $stat->{cpu};
>  	$res->{wait} = $stat->{wait};
>  
> +	if (my $fh = IO::File->new ("/proc/stat", "r")) {

nit: Minor note, but there shouldn't be a space between the function's 
name and its parameter list [0].

> +	    my ($uptime_ticks) = PVE::ProcFSTools::read_proc_uptime(1);
> +	    while (defined (my $line = <$fh>)) {
> +		if ($line =~ m|^cpu\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)(?:\s+(\d+)\s+(\d+))?|) {
> +		    $res->{cpustat}->{user} = int($1);
> +		    $res->{cpustat}->{nice} = int($2);
> +		    $res->{cpustat}->{system} = int($3);
> +		    $res->{cpustat}->{idle} = int($4);
> +		    $res->{cpustat}->{iowait} = int($5);
> +		    $res->{cpustat}->{irq} = int($6);
> +		    $res->{cpustat}->{softirq} = int($7);
> +		    $res->{cpustat}->{steal} = int($8);
> +		    $res->{cpustat}->{guest} = int($9);
> +		    $res->{cpustat}->{guest_nice} = int($10);
> +		    $res->{cpustat}->{uptime_ticks} = $uptime_ticks;

nit: I think this could be placed rather nicely at 
`$res->{uptime_ticks}`, like `$res->{uptime}`, to make `cpustat` a 
little more consistent with `PVE::ProcFSTools::read_proc_stat()` and

> +		} elsif ($line =~ m|^cpu(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)(?:\s+(\d+)\s+(\d+))?|) {
> +		    $res->{cpustat}->{"cpu" . $1}->{user} = int($2);
> +		    $res->{cpustat}->{"cpu" . $1}->{nice} = int($3);
> +		    $res->{cpustat}->{"cpu" . $1}->{system} = int($4);
> +		    $res->{cpustat}->{"cpu" . $1}->{idle} = int($5);
> +		    $res->{cpustat}->{"cpu" . $1}->{iowait} = int($6);
> +		    $res->{cpustat}->{"cpu" . $1}->{irq} = int($7);
> +		    $res->{cpustat}->{"cpu" . $1}->{softirq} = int($8);
> +		    $res->{cpustat}->{"cpu" . $1}->{steal} = int($9);
> +		    $res->{cpustat}->{"cpu" . $1}->{guest} = int($10);
> +		    $res->{cpustat}->{"cpu" . $1}->{guest_nice} = int($11);
> +		}
> +	    }
> +	    $fh->close;
> +	}

Is there something that is holding us back to move this directly into 
`PVE::ProcFSTools::read_proc_stat()`?

As far as I can tell, the output of `PVE::ProcFSTools::read_proc_stat()` 
is used at these locations:

- the PVE `/nodes/{node}/status` API endpoint of course, which only uses 
the values of `cpu` and `wait` at the moment
- `PMG::API2::Nodes`: also only uses the values of `cpu` and `wait`
- the PMG `/nodes/{node}/status` API endpoint, which also only uses the 
values of `cpu` and `wait`
- `PVE::Service::pvestatd::update_node_status`: retrieve the current 
node status and then update them for rrd via `broadcast_rrd` (uses only 
the values of `cpu` and `wait` selectively) and external metric servers

The first three and a half (speaking of `broadcast_rrd` in the latter) 
look fine to me, but we should take a closer look how external metric 
servers will handle the added data, especially for existing 
queries/dashboards. It could also be a name collision, as 'cpustat' is 
also used for the data that gets sent to the metric servers.

In my opinion, I think it would be a worthwhile feature to add the 
properties for external metric servers (either as part of this or a 
future patch series).

> +
>  	my $meminfo = PVE::ProcFSTools::read_meminfo();
>  	$res->{memory} = {
>  	    free => $meminfo->{memfree},
> -- 
> 2.46.0
It would also be very beneficial if the added data properties that are 
returned here are documented in the 'returns' JSONSchema, so that they 
can be easily understood by other users as well (especially in which 
unit those raw values are so that it's easier to know how they would 
need to get converted).

---

Otherwise, this works just as intended when querying the API endpoint 
`/nodes/{node}/status` via curl and pvesh.

Reviewed-by: Daniel Kral <d.kral@proxmox.com>
Tested-by: Daniel Kral <d.kral@proxmox.com>

[0] https://pve.proxmox.com/wiki/Perl_Style_Guide#Spacing_and_syntax_usage


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