ig has asked for the wisdom of the Perl Monks concerning the following question:
If I use system to run cat to display the contents of /proc/$$/smaps or if I open it with PerlIO layer :stdio, there is only one vdso vm area listed. For example:
But if I use the default PerlIO layer(s), then it appears that smaps has two vdso vm areas. For example:#!/usr/bin/perl use strict; use warnings; my $file = "/proc/$$/smaps"; open(my $f, '<:stdio', $file) or die "$file: $!"; my $smaps = do { local $/; <$f> }; close($f); print "$smaps\n";
#!/usr/bin/perl use strict; use warnings; my $file = "/proc/$$/smaps"; open(my $f, '<', $file) or die "$file: $!"; my $smaps = do { local $/; <$f> }; close($f); print "$smaps\n";
There are other differences than the number of vdso vm areas, but I assume those are because the different PerlIO layers use memory differently.
The two vdso vm areas appear to be identical, so I wonder if this is an artifact of PerlIO rather than the content of /proc/$$/smaps.
update: The problem is not with Perl. It varies with how /proc/$$/smaps is read, but duplicate vdso areas can be observed with other readers. For example: grep . /proc/$$/smaps. It occurs with Linux kernel 2.6.25.3 but not with 2.6.23.1-21.1 (Redhat).
Perlbug -d produces the following on my system:
--- Flags: category= severity= --- This perlbug was built using Perl v5.8.8 in the Red Hat build system. It is being executed now by Perl v5.8.8 - Mon Nov 12 14:44:38 EST 2007 +. Site configuration information for perl v5.8.8: Configured by Red Hat, Inc. at Mon Nov 12 14:44:38 EST 2007. Summary of my perl5 (revision 5 version 8 subversion 8) configuration: Platform: osname=linux, osvers=2.6.20-1.3002.fc6xen, archname=i386-linux-thr +ead-multi uname='linux xenbuilder1.fedora.redhat.com 2.6.20-1.3002.fc6xen #1 + smp mon aug 13 14:21:21 edt 2007 i686 athlon i386 gnulinux ' config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOU +RCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 - +march=i386 -mtune=generic -fasynchronous-unwind-tables -Dversion=5.8. +8 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by= +Red Hat, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Darchname=i386-linu +x -Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads -Du +seithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndb +m -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallu +srbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr +-Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto +-Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_prot +o -Ud_setservent_r_proto -Dinc_version_list=5.8.7 5.8.6 5.8.5 -Dscrip +tdir=/usr/bin' hint=recommended, useposix=true, d_sigaction=define usethreads=define use5005threads=undef useithreads=define usemulti +plicity=define useperlio=define d_sfio=undef uselargefiles=define usesocks=undef use64bitint=undef use64bitall=undef uselongdouble=undef usemymalloc=n, bincompat5005=undef Compiler: cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasin +g -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFI +LE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm', optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions +-fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=g +eneric -fasynchronous-unwind-tables', cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -W +declaration-after-statement -I/usr/local/include -I/usr/include/gdbm' ccversion='', gccversion='4.1.2 20070925 (Red Hat 4.1.2-27)', gcco +sandvers='' intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234 d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1 +2 ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', + lseeksize=8 alignbytes=4, prototype=define Linker and Libraries: ld='gcc', ldflags =' -L/usr/local/lib' libpth=/usr/local/lib /lib /usr/lib libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread +-lc perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc libc=/lib/libc-2.6.so, so=so, useshrplib=true, libperl=libperl.so gnulibc_version='2.6' Dynamic Linking: dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E - +Wl,-rpath,/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE' cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_F +ORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-siz +e=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -L/u +sr/local/lib' Locally applied patches: --- @INC for perl v5.8.8: /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.7/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.6/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.5/i386-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib/perl5/vendor_perl/5.8.8/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.7/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.6/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.5/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib/perl5/5.8.8/i386-linux-thread-multi /usr/lib/perl5/5.8.8 . --- Environment for perl v5.8.8: HOME=/home/ian LANG=en_US.UTF-8 LANGUAGE (unset) LD_LIBRARY_PATH (unset) LOGDIR (unset) PATH=/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin +:/home/ian/bin:/sbin PERL_BADLANG (unset) SHELL=/bin/bash
|
|---|
| Replies are listed 'Best First'. | |
|---|---|
|
Re: /proc/$$/smaps, PerlIO and vdso
by ig (Vicar) on Jun 03, 2008 at 18:54 UTC |