Re: Removing dbregs

[Jason Thorpe <thorpej%me.com@localhost>]

> On Jul 13, 2018, at 2:22 PM, Kamil Rytarowski <n54%gmx.com@localhost> wrote:
> 
> On 13.07.2018 23:10, Jaromír Doleček wrote:
>> 2018-07-13 22:54 GMT+02:00 Kamil Rytarowski <n54%gmx.com@localhost>:
>>> I disagree with disabling it. The code is not broken, it's covered by
>>> tests, it's in use.
>> 
>> This looks like perfect candidate for optional (default off) feature.
>> It is useless and dangerous for general purpose use by virtue of being
>> root only, but useful for specialized use.
>> 
>> Honestly, I don't see any reason to have this on by default.

A sysctl is kind of lame, because it can also result in a branch prediction miss.

Protect the sysctl in an #ifdef to enable being able to enable the feature?

>> 
>> Jaromir
>> 
> 
> We have got this state now. It's a trade-off that we disable it for
> user, and keep for root and those who use it (sysctl switch).
> 
> I agree that there might be a microoptimization with not reloading DR,
> but there is a bigger fish to fry at this point rather than winning 0,3%
> of performance by killing a feature that is in use.
> 
> If anything, the proper solution is to optimize the register switch.
> 

-- thorpej