R11B multiple processes starting

Ryan Rawson <>
Tue Jul 11 00:54:49 CEST 2006


The way the OS handles threads changed from 2.4 to kernel 2.6.  No
longer in 2.6 do you see multiple entries in the process table for
threads.  It's now 'hidden' in one big process id, and there are
thread ids.

-ryan

On 7/7/06, Michael McDaniel <> wrote:
> Thank you for that explanation.  I do see
>
> $ ls /lib/*pthread*
> /lib/libpthread.so.0
>
> $ ls /usr/lib/*pthread*
> /usr/lib/libpthread.a  /usr/lib/libpthread_nonshared.a  /usr/lib/libpthread.so
>
> on the original machine in which 'ps' shows multiple OS processes
> (it has a 2.4 kernel with Pentium 4 processor)
>
>
> New information is that on another machine (2.6 kernel with Celeron processor)
> (again, R11B-0 compiled *without* --enable-smp-support)
>
> $ uname -a
> Linux cougora 2.6.4-52-default #1 Wed Apr 7 02:08:30 UTC 2004 i686 i686 i386 GNU/Linux
>
> $ ls /lib/*pthread*
> /lib/libpthread.so.0
>
> $ ls /usr/lib/*pthread*
> /usr/lib/libgcrypt-pthread.a   /usr/lib/libgcrypt-pthread.so.7      /usr/lib/libpthread_nonshared.a
> /usr/lib/libgcrypt-pthread.la  /usr/lib/libgcrypt-pthread.so.7.3.1  /usr/lib/libpthread.so
> /usr/lib/libgcrypt-pthread.so  /usr/lib/libpthread.a
>
> and, starting the same application in the same manner, it only shows
> a single process.
>
> So, a new question is why might those machines be different?
>
>
>
> ~~Michael
>
>
> On Fri, Jul 07, 2006 at 06:36:21PM -0700, Ryan Rawson wrote:
> > All modern Linux distros have pthread libraries in /lib now if not
> > /usr/lib that are posix threads that are native.  Linux models those
> > threads as light weight processes - thus appear as multiple entries in
> > the process table.
> >
> > R11B-0 included the SMP improvements, and also I think threading
> > improvements for lower level driver things.  Blocking IO and the like
> > I think.  Someone else can give a detailed view on that, but I believe
> > that is the high level.
> >
> > -ryan
> >
> > On 7/7/06, Michael McDaniel <> wrote:
> > >SHORT VERSION:
> > >
> > >After installing R11B-0, my application starts multiple OS processes
> > >where before it only started a single OS process.
> > >-----------
> > >
> > >
> > >LONG VERSION:
> > >
> > >I have just installed R11B-0 on one of my servers (formerly at R10B-8).
> > >
> > >$ uname -a
> > >Linux xq02 2.4.21-99-default #1 Wed Sep 24 13:30:51 UTC 2003 i686 i686
> > >i386 GNU/Linux
> > >
> > >
> > >An application that I start thusly:
> > >
> > >$ /bin/su mmcdanie -c "cd /home/erl ; /usr/local/bin/erl -sname   \
> > >   ${HOST}_block -home /home/erl -setcookie fake -heart -detached \
> > >   -config /home/erl/sys.config  -s block start"
> > >
> > >is still working fine.  However, now when I start it, three OS
> > >processes are running rather than as with R10B-8 where only a
> > >single OS process would run when application started.
> > >
> > >$ ps xuaw | egrep block | egrep -v grep
> > >mmcdanie 14771  0.1  1.2 12964 6440 pts/1    S    15:59   0:00
> > >/usr/local/lib/erlang/erts-5.5/bin/beam -- -root /usr/local/lib/erlang
> > >-progname erl -- -home /home/mmcdanie -sname xq02_block -home /home/erl
> > >-setcookie fake -heart -noshell -noinput -config /home/erl/sys.config -s
> > >block start
> > >mmcdanie 14774  0.0  1.2 12964 6440 pts/1    S    15:59   0:00
> > >/usr/local/lib/erlang/erts-5.5/bin/beam -- -root /usr/local/lib/erlang
> > >-progname erl -- -home /home/mmcdanie -sname xq02_block -home /home/erl
> > >-setcookie fake -heart -noshell -noinput -config /home/erl/sys.config -s
> > >block start
> > >mmcdanie 14775  0.0  1.2 12964 6440 pts/1    S    15:59   0:00
> > >/usr/local/lib/erlang/erts-5.5/bin/beam -- -root /usr/local/lib/erlang
> > >-progname erl -- -home /home/mmcdanie -sname xq02_block -home /home/erl
> > >-setcookie fake -heart -noshell -noinput -config /home/erl/sys.config -s
> > >block start
> > >
> > >(apologies for line wraps)
> > >
> > >I am not understanding why multiple OS processes are running now when
> > >I start the application.  I have changed nothing on the machine other
> > >than installing the new R11B-0  (and the way I did that was to move
> > >the old /usr/local/lib/erlang directory before doing the install, so
> > >the new /usr/local/lib/erlang is completely fresh, not an
> > >install-over-old).
> > >
> > >As I mention above, the application is working fine.
> > >
> > >The contents of /home/erl/sys.config are:
> > >[{mnesia, [{dir, "/home/erl/Mnesia.block"}  ,
> > >%%           {debug, trace}                   ,
> > >           {schema_location, disc}]}].
> > >
> > >and mnesia is getting updated just fine.
> > >
> > >I compiled *without* --enable-smp-support since the native POSIX threads
> > >library is not installed (it is not an SMP machine).
> > >
> > >
> > >Does anyone have any tips on how to figure out why multiple OS processes
> > >are now starting?  Or perhaps already knows the answer to the question?
> > >
> > >thanks,
> > >
> > >~Michael
> > >
> > >
> > >
> > >
>
> --
> Michael McDaniel
> Portland, Oregon, USA
> http://autosys.us
> +1 503 283 5284
>



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