RFC: system-wide default tunables

[Siddhesh Poyarekar]

On 2023-10-17 12:45, DJ Delorie wrote:
> Siddhesh Poyarekar <siddhesh@gotplt.org> writes:
>> Only stricter overrides to systemwide tunables should be allowed,
> 
> This leads to the next question: how to express these constraints in the
> tunables.conf file.  A the simplest, prefixing each tunable with '+',
> '-', or '=' for example?  For stricter, looser, or can't change?  Else
> we need to come up with some more flexible "flag parser".
> 

Actually I wasn't thinking of any conf file related constraint markup, I 
was thinking of TUNABLE_CALLBACKs encoding constraints in whichever way 
they deem fit.  e.g. for ibt it could be:

void
TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *valp)
{
   if (!strcmp (valp->system_default, "always_on"))
     return;

   /* Otherwise read the value.  */
}