[systemd-devel] Significant performance loss caused by commit a65f06b: journal: return -ECHILD after a fork

[Lennart Poettering]

On Tue, 11.07.17 12:55, Uoti Urpala (uoti.urpala at pp1.inet.fi) wrote:

> On Tue, 2017-07-11 at 09:35 +0200, Lennart Poettering wrote:
> > Normally it's dead cheap to check that, it's just reading and
> > comparing one memory location. It's a pitty that this isn't the case
> > currently on Debian, but as it appears this is an oversight on their
> > side, and I am sure it will be eventually fixed there, if it hasn't
> > already.
> 
> Are you sure about those "Debian only" and "will be 'fixed'" parts? The
> Debian patch seems to be a cherry pick from upstream glibc. Is there
> evidence of some error that would cause effects only visible on Debian
> and nowhere else? And/or has the change been reverted or behavior
> otherwise modified upstream to limit the range of relevant versions?

See the links Vito provided:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=857909
https://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commit;h=0cb313f7cb0e418b3d56f3a2ac69790522ab825d

i.e. Debian undid the PID caching to fix some issue that has been fix
properly now, and hence the PID caching should be turned on again.

On Fedora at least getpid() is not visible in strace, and is fully
cached, as it should be.

Lennart

-- 
Lennart Poettering, Red Hat