Re: About ceph_clock_now()

[Willem Jan Withagen <wjw@digiware.nl>]

On 25-1-2016 10:58, Erwan Velu wrote:
>> I would comment the last section: the #else with a remark that you
>> select POSIX if nothing else, but that POSIX is more/unneeded accurate
>> and slow.
>
> I totally agree with your comment.
> I'm pretty boring on that topic but keeping a well documented commit (in the commit message) that explains the following is very useful when reading a patch later.
> - what was the issue
> - how we fixed it

I would even keep it in the code so that somebody looking at it understands
that the system default for a reason to slower POSIX.
Especially in porting circumstances this is important.
And even more so, now it is almost impossible to detect this compiletime.

I ran into it bacause only one option was there: *COARSE, so my build 
bombed out.
Now it it will select the slow POSIX if I don not have *COARSE or *FAST, 
and
merrily compile on.

So you'd only find this then running benchmarks and notice significant 
slowdown.

Come to think of it, it might even warrant a #warning line in the POSIX 
case,
to suggest to look into the 'man clock_gettime' page and see if the new 
OS has
something better.

--WjW