From: Atanas Vladimirov <vlado@bsdbg.net>
Subject: Re: Telegraf mem plugin and OpenBSD Cache memory
To: ports@openbsd.org
Date: Sat, 21 Feb 2026 14:30:49 +0200

Morning,

I would appreciate any input on this :)

Best wishes,
Atanas

On 2026-02-18 15:58, Atanas Vladimirov wrote:
> Hello,
> 
> I need your advice on something I just found.
> The short version is I started migrating from node_exporter to Telegraf 
> and found discrepancy between how Telegraf reports memory usage 
> compared to node_exporter.
> 
> I have come with this Telegraf patch:
> 
> ```
> Index: plugins/inputs/mem/mem.go
> --- plugins/inputs/mem/mem.go.orig
> +++ plugins/inputs/mem/mem.go
> @@ -50,7 +50,7 @@ func (ms *Mem) Gather(acc telegraf.Accumulator) error
>                 fields["wired"] = vm.Wired
>         case "openbsd":
>                 fields["active"] = vm.Active
> -               fields["cached"] = vm.Cached
> +               fields["cached"] = vm.Buffers
>                 fields["free"] = vm.Free
>                 fields["inactive"] = vm.Inactive
>                 fields["wired"] = vm.Wired
> ```
> 
> It works.
> 
> The problem is that Telegraf reports cached = 0 because gopsutil sets 
> Cached = 0.
> 
> Here is the gopsutil part
> https://github.com/shirou/gopsutil/blob/67304c33f246d9598551d61af85690d50b3e8606/mem/mem_openbsd.go#L41
> ```
> ret := &VirtualMemoryStat{
>     Total:    uint64(uvmexp.Npages) * p,
>     Free:     uint64(uvmexp.Free) * p,
>     Active:   uint64(uvmexp.Active) * p,
>     Inactive: uint64(uvmexp.Inactive) * p,
>     Cached:   0, // not available   <-- explicitly hardcoded
>     Wired:    uint64(uvmexp.Wired) * p,
> }
> ```
> 
> The above patch uses `vm.Buffers` from gopsutil and this is what 
> node_exporter does.
> 
> I'm almost sure that you'll say that this should go upstream, right?
> 
> My question is where should I try to send the patch - to Telegraf or to 
> gopsutil? What would you suggest?
> 
> (a patch for the gopsutil would be something like adding:
> 
> ```
> ret.Cached = ret.Buffers    <-- adds the Cached to be equal to Buffers
> ```
> 
> of course, if this is the path I'll see to check and test it more)
> 
> Thanks for you time and please add me in CC to the replies because I'm 
> not subscribed to the list.
> 
> Best wishes,
> Atanas