A single environment variable for tunables vs a variable per tunable

[Carlos O'Donell]

On 09/17/2015 01:59 PM, Siddhesh Poyarekar wrote:
> On Thu, 2015-09-17 at 10:51 -0700, Roland McGrath wrote:
>> There should be no explicit code using new environment variables at
>> all.
>> It should all go through the tunables framework so policy and
>> knowledge
>> about use of environment variables is centralized.
> 
> I pushed some code to the siddhesh/tunables branch last week that reads
> just one magic environment variable and parses the string to initialize
> all tunables at once.  This gives a definite path to deprecate the
> existing arbitrary environment variables in future as well since it
> clearly separates those bits from the core framework.  So now y'all
> have both approaches to try out while I cool my heels off for a bit - I
> hope to be back hacking soon.
> 
> We have talked about both approaches for a bit in different threads and
> I continue to have a slight preference for the single environment
> variable for the sheer ease of initialization and the possibility of
> doing it really early once I figure out how to get the code included
> into the dynamic linker without dropping it into the elf directory. 
>  All other differences seem cosmetic to me.

Given that we can change our mind on a release-by-release basis I'm also
happy with just one env var... given that you implemented it :-)

c.