On Tue, Jul 11, 2017 at 09:59:45PM +1000, Michael Chapman wrote: > On Tue, 11 Jul 2017, Lennart Poettering wrote: > >On Tue, 11.07.17 12:55, Uoti Urpala (uoti.urp...@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. > > I just tested this on F25 and F26 beta, and it's certainly visible > for me on both of them: > > # cat /etc/system-release > Fedora release 25 (Twenty Five) > # rpm -q glibc > glibc-2.24-9.fc25.x86_64 > # strace -c journalctl --since -1hour 2>&1 >/dev/null | head -10 > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 93.93 0.167020 2 83761 getpid > 3.93 0.006983 2 3025 write > 0.54 0.000953 10 97 mmap > 0.39 0.000696 13 52 8 open > 0.31 0.000558 14 40 munmap > 0.19 0.000332 8 42 mprotect > 0.15 0.000264 6 45 fstat > 0.14 0.000246 6 44 close > > # cat /etc/system-release > Fedora release 26 (Twenty Six) > # rpm -q glibc > glibc-2.25-7.fc26.x86_64 > # strace -c journalctl --since -1hour 2>&1 >/dev/null | head -10 > % time seconds usecs/call calls errors syscall > ------ ----------- ----------- --------- --------- ---------------- > 62.84 0.007874 4 2063 getpid > 7.96 0.000998 12 86 mmap > 7.85 0.000983 20 48 8 open > 3.85 0.000483 9 54 mprotect > 2.80 0.000351 5 71 write > 2.75 0.000345 11 32 read > 2.69 0.000337 8 41 fstat > 2.66 0.000333 8 40 close > > The second machine had just been started, which is why the numbers > are a lot lower. Nevertheless, getpid is still taking by far the > most amount of time in syscalls. > > Both of these are on Fedora's testing branch, but I don't think > Fedora's regular branch has a significantly different version of > glibc.
Yep, I can confirm that: many many getpid() syscalls on F26 and rawhide, and none on F24. Zbyszek _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
