Re: large overhead in libmount

[Karel Zak <kzak@redhat.com>]

On Tue, Jan 20, 2015 at 02:01:13AM +0000, Pádraig Brady wrote:
> On 30/12/14 22:06, Bernhard Voelker wrote:
> > I just pulled the recent gnulib update, and now the above, expensive
> > test fails:
> > 
> >    + ulimit -v 40000
> >    + du -sh d
> >    du: fts_read failed: d: Cannot allocate memory
> >    + fail=1
> > 
> > I guess this due to the inclusion of libmount?
> 
> Yes I get the same issue in that test:
> http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=blob;f=tests/rm/many-dir-entries-vs-OOM.sh
> 
> Indeed there is significant overhead in using libmount as shown below.
> This is a crazy amount of overhead just to read /proc/self/mountinfo,
> and is the sort of creeping dependencies I hate.  The proposed solution
> in the attached gnulib patch, is to require ./configure --with-libmount
> to enable this feature. I.E. it's disabled by default.
> 
> cheers,
> Pádraig
> 
> ======= without =========
> $ (ulimit -v 5380; du -s .)
> 
> $ ldd /usr/bin/du
> linux-vdso.so.1 =>  (0x00007fff0d7fe000)
> libc.so.6 => /lib64/libc.so.6 (0x00007fd414a32000)
> /lib64/ld-linux-x86-64.so.2 (0x00007fd414e0b000)
> 
> $ time du -s src/du.c >/dev/null
> real    0m0.003s
> user    0m0.000s
> sys     0m0.003s
> 
> ======= with =========
> $ (ulimit -v 23250; src/du -s .)
> 
> $ ldd src/du
> linux-vdso.so.1 =>  (0x00007fff76ca8000)
> libc.so.6 => /lib64/libc.so.6 (0x00007f2a1f742000)
> /lib64/ld-linux-x86-64.so.2 (0x00007f2a1fd61000)
>  libmount.so.1 => /lib64/libmount.so.1 (0x00007f2a1faff000)
>   libblkid.so.1 => /lib64/libblkid.so.1 (0x00007f2a1f501000)
>   libuuid.so.1 => /lib64/libuuid.so.1 (0x00007f2a1f2fc000)
>   libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f2a1f0d7000)
>   libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f2a1ee69000)
>   liblzma.so.5 => /lib64/liblzma.so.5 (0x00007f2a1ec44000)
>   libdl.so.2 => /lib64/libdl.so.2 (0x00007f2a1ea40000)
>   libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f2a1e823000)

The problem is libselinux, but on selinux based system you have all the
libraries already in memory for many another tools...

    Karel
-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com