Re: [gentoo-dev] Defining TZ in the base system profile?

[Arsen Arsenović]

Michał Górny <mgorny@g.o> writes:

> On Wed, 2023-01-18 at 20:48 -0500, Joshua Kinard wrote:
>> So this article[1] from 2017 popped up again on the tech radar via hackernews[2] and a few other sites[3].  It
>> annotates how if the envvar TZ is undefined on a Linux system, it causes glibc to generate a number of
>> additional syscalls, mainly stat-related calls (in my tests, newfstatat()).  If defined to an actual value,
>> such as ":/etc/localtime" (or even an empty string), glibc will instead generate far fewer, if any at all, of
>> these stat-related syscalls.
>>
>> [...]
>> So is adding a default definition of TZ to our base system /etc/profile something we want to look at?  I
>> haven't tried any other methods of benchmarking to see if not making those additional syscalls is just placebo
>> or if there are actual impacts.  Given how long this oddity has been around, I can't tell if it's a genuine
>> bug in glibc, an unoptimized corner case, or just a big nothingburger.
>>
>
> Am I correct that there's no real difference between setting it to
> ":/etc/localtime" and the actual timezone?
>
> I suppose it would make sense to default it.

Correct, from ``(libc)TZ Variable'':

   If the ‘TZ’ environment variable does not have a value, the operation
chooses a time zone by default.  In the GNU C Library, the default time
zone is like the specification ‘TZ=:/etc/localtime’ (or
‘TZ=:/usr/local/etc/localtime’, depending on how the GNU C Library was
configured; *note Installation::).  Other C libraries use their own rule
for choosing the default time zone, so there is little we can say about
them.

I don't suspect any downside to this approach.
-- 
Arsen Arsenović