Re: [PATCH net-next] tools: ynl: try to avoid the very slow YAML loader

[Jacob Keller <jacob.e.keller@intel.com>]

On 6/3/2026 2:08 PM, Jakub Kicinski wrote:
> Turns out Python YAML defaults to a pure Python loader for YAML
> files which is a lot slower than the C loader (using libyaml).
> Try to use the C one whenever possible.
> 
> The avg time to run:
>   $ tools/net/ynl/pyynl/cli.py --family tc --no-schema
> drops from 300+ ms to 115 ms with this change (40 samples).
> 
> We could drop the load time further to 85 ms if we "compiled"
> the specs to JSON. Slightly tricky parts are that we don't
> currently install the specs at all on make install, so it's
> unclear where to put the conversion. Also JSON has questionable
> support for comments and we need an SPDX line.
> > Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: donald.hunter@gmail.com
> ---
>  tools/net/ynl/pyynl/lib/nlspec.py | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/net/ynl/pyynl/lib/nlspec.py b/tools/net/ynl/pyynl/lib/nlspec.py
> index fcffeb5b7ba3..0469a0e270d0 100644
> --- a/tools/net/ynl/pyynl/lib/nlspec.py
> +++ b/tools/net/ynl/pyynl/lib/nlspec.py
> @@ -439,6 +439,11 @@ import yaml as pyyaml
>      # To be loaded dynamically as needed
>      jsonschema = None
>  
> +    try:
> +        _yaml_loader = pyyaml.CSafeLoader
> +    except AttributeError:
> +        _yaml_loader = pyyaml.SafeLoader
> +
>      def __init__(self, spec_path, schema_path=None, exclude_ops=None):
>          with open(spec_path, "r", encoding='utf-8') as stream:
>              prefix = '# SPDX-License-Identifier: '
> @@ -448,7 +453,7 @@ import yaml as pyyaml
>              self.license = first[len(prefix):]
>  
>              stream.seek(0)
> -            spec = pyyaml.safe_load(stream)
> +            spec = pyyaml.load(stream, Loader=self._yaml_loader)
>  
Hmm. I was a bit confused at first by the switch from safe_load to
load.. but we're passing Loader as _yaml_loader which will either be
CSafeLoader *or* the default SafeLoader, so we'll get the appropriate
loader equivalent to what safe_load would have done, so there's no
change. Ok

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

>          self.fixed_header = None
>          self._resolution_list = []
> @@ -464,7 +469,7 @@ import yaml as pyyaml
>              schema_path = os.path.dirname(os.path.dirname(spec_path)) + f'/{self.proto}.yaml'
>          if schema_path:
>              with open(schema_path, "r", encoding='utf-8') as stream:
> -                schema = pyyaml.safe_load(stream)
> +                schema = pyyaml.load(stream, Loader=self._yaml_loader)
>  
>              if SpecFamily.jsonschema is None:
>                  SpecFamily.jsonschema = importlib.import_module("jsonschema")