Re: CVS commit: src/sys

[Greg Troxel <gdt%lexort.com@localhost>]

Ryota Ozaki <ozaki-r%netbsd.org@localhost> writes:

> On Tue, May 14, 2019 at 2:31 AM Jason Thorpe <thorpej%me.com@localhost> wrote:
>>
>>
>>
>> > On May 13, 2019, at 7:17 AM, Greg Troxel <gdt%lexort.com@localhost> wrote:
>> >
>> > 2) Your option 2 seems to involve two things at once:
>> >
>> >  - migration to lwp_specificadata
>> >  - using DEBUG instead of DIAGNOSTIC to control the leak check feature
>> >
>> > I do not understand why changing the nature of the implementation is
>> > linked to how it is enabled.
>>
>> I think Ozaki-san saying that the 3% performance hit only happens
>> when lwp_specificdata is used, and hence that it would need to be
>> wrapped in DEBUG rather than DIAGNOSTIC.

Now this is all making sense.

>> The original negligible-impact implementation did NOT use
>> lwp_specificdata, and thus was fine for DIAGNOSTIC.  I believe
>> Ozaki-san's preference is to use *this* implementation so that it
>> can be exposed to a wider audience.  The lwp_specificdata approach
>> was only explored after someone else suggested a preference for it.
>>
>> At least, that's my understanding of the situation.
>
> Yes, your understanding is correct.  Thank you for the clarification.

So having a check under DIAGNOSTIC that you more or less can't measure
sounds just fine to me.  I only meant to object to a 3% slowdown under
DIAGNOSTIC.

And, if someone is inclined, having better checks with meaurable
slowdown under DEBUG sounds ok too, but my revised understanding is
unclear on whether that's helpful.  (But I am only trying to keep
performance under DIAGNOSTIC high; I am unconcerned about DEBUG and
don't need to understand.)