netdev - Re: [PATCH iproute2-next 2/3] ip link: Drop cache entry on name changes

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Date:   Mon, 7 Jan 2019 17:26:27 -0700
From:   David Ahern <dsahern@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>,
        David Ahern <dsahern@...nel.org>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2-next 2/3] ip link: Drop cache entry on name
 changes

On 1/7/19 5:06 PM, Stephen Hemminger wrote:
> On Mon,  7 Jan 2019 14:55:51 -0800
> David Ahern <dsahern@...nel.org> wrote:
> 
>> +int iplink_parse(int argc, char **argv, struct iplink_req *req, char **type,
>> +		 bool *name_change);
> 
> Not a real fan of adding another by reference return value flag.
> It makes the logic flow more complex.
> 
> Is there another way? Caching in general is dicey anyway.
> 

The details of the link change are buried inside of the req argument. It
does not make sense to decode the message to see if the devices
referenced by ifi_index == IFLA_NAME.

The alternative is to just negate caching of ifi_index regardless of
what the request is doing.

If the caching only gained 5 or 10% we would not be having this
discussion - I would not have sent patches. The gain here is significant
and the caching aligns with the whole intent of batch files.