Date: Fri, 12 Apr 2019 12:41:53 +0200 From: Dima Pasechnik <dimpase+freebsd@gmail.com> To: Alexander Zagrebin <alex@zagrebin.ru> Cc: FreeBSD Ports <freebsd-ports@freebsd.org> Subject: Re: python 3 subprocess performance Message-ID: <CAAWYfq16Y90-nXeV3TkT10uh=_tK=Vgjk_QEJo=DM-P8KGFNQg@mail.gmail.com> In-Reply-To: <20190412104531.7b492a3c@vm2.home.zagrebin.ru> References: <20190411161649.1b740d21@vm2.home.zagrebin.ru> <8f3f8413-60f2-bb03-a6b4-4f6364cdc3df@rlwinm.de> <20190411143926.5rg4jskmodt4shhi@laparbeit> <9729db47-12c4-caf4-cdcf-1913dab73c8e@rlwinm.de> <20190412101012.4142854f@vm2.home.zagrebin.ru> <CAAWYfq2P5QsSbc2bzQauApF6=ijQYpKCb2HQ1jy-4dNZCOB_=g@mail.gmail.com> <20190412104531.7b492a3c@vm2.home.zagrebin.ru>
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On Fri, Apr 12, 2019 at 9:46 AM Alexander Zagrebin <alex@zagrebin.ru> wrote= : > > =D0=92 Fri, 12 Apr 2019 09:36:13 +0200 > Dima Pasechnik <dimpase+freebsd@gmail.com> =D0=BF=D0=B8=D1=88=D0=B5=D1=82= : > > > On Fri, Apr 12, 2019 at 9:11 AM Alexander Zagrebin <alex@zagrebin.ru> > > wrote: > > > > > > =D0=92 Thu, 11 Apr 2019 17:32:42 +0200 > > > Jan Bramkamp <crest@rlwinm.de> =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > > > > > > The reason is that that python does something stupid (tm). It > > > > tries to close all file descriptors (except a few whitelisted > > > > ones) up to the maximum file descriptor number. It does this by > > > > asking the kernel for the maximum possible number and closing > > > > everything it doesn't want to keep. Some time later someone came > > > > up with an optimization (read the open file descriptors > > > > from /dev/fd). All of this pain and suffering is caused by good > > > > old Ulrich Drepper braindamage: > > > > https://sourceware.org/bugzilla/show_bug.cgi?id=3D10353. > > > > > > > > Most Linux distros have lower default file descriptor limits than > > > > FreeBSD making this workaround less painful. The correct solution > > > > would be to teach python3 about closefrom(2). > > > > > > Thank you for hint and testing! > > > > > > Indeed the problem is in closing more than 400,000 file descriptors > > > in loop. It seems that all current versions of Python are affected. > > > Python2 uses False as default value for the close_fds parameter of > > > the Popen constructor, so this issue is mostly not visible. > > > Python3 has changed this default to True. > > > > > > As Jan Bramkamp suggested, I've wrote simple patch to fix an issue > > > (see attached file). It seems the problem has gone. > > > > The attachment has been stripped out. Could you paste the diff into > > the message? > > Yes, sure. > > --- Modules/_posixsubprocess.c.orig 2018-12-24 00:37:14.000000000 > +0300 +++ Modules/_posixsubprocess.c 2019-04-12 > 09:25:21.549389000 +0300 @@ -235,11 +235,15 @@ > _close_fds_by_brute_force(long start_fd, } > start_fd =3D keep_fd + 1; > } > +#if defined(__FreeBSD__) > + closefrom(start_fd); > +#else > if (start_fd <=3D end_fd) { > for (fd_num =3D start_fd; fd_num < end_fd; ++fd_num) { > close(fd_num); > } > } > +#endif > } > > > If this is a Python issue, shouldn't this be reported upstream, on > > https://bugs.python.org ? > > May be. Rather, it is a FreeBSD-specific optimization. Well, closefrom() is also available in Darwin (a.k.a. MacOSX :-)), OpenBSD and NetBSD. (It's not documented in current MacOSX, but it is there, I just checked) Anyway, FreeBSD Python maintainers will ask for an upstream PR. I can do such a PR is noone else is willing to... Dima > > -- > Alexander Zagrebin > _______________________________________________ > freebsd-ports@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-ports > To unsubscribe, send any mail to "freebsd-ports-unsubscribe@freebsd.org"
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