<!-- Copyright (c) 2015 The President and Fellows of Harvard College. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. --> <html> <head> <title>multiexec</title> <link rel="stylesheet" type="text/css" media="all" href="../man.css"> </head> <body bgcolor=#ffffff> <h2 align=center>multiexec</h2> <h4 align=center>OS/161 Reference Manual</h4> <h3>Name</h3> <p> multiexec - run many exec calls at once </p> <h3>Synopsis</h3> <p> <tt>/testbin/multiexec</tt> [-j <em>nprocs</em>] [<em>prog</em> [<em>arg</em> ...]] </p> <h3>Description</h3> <p> <tt>multiexec</tt> forks several subprocesses and then uses user-level semaphores to cause them to all enter <A HREF=../syscalls/execv>execv</A> at as close as possible to the same time. This is useful for seeing what happens if having too many argv buffers in use at once causes the kernel to run into problems, or to test the efficacy of measures to mitigate those problems. </p> <p> The default number of subprocesses is 12. The default program each subprocess runs is <A HREF=../bin/pwd.html>pwd</A>. Other larger programs can be run by giving the program name and arguments on <tt>multiexec</tt>'s command line. </p> <h3>Requirements</h3> <p> <tt>multiexec</tt> uses the following system calls: <ul> <li><A HREF=../syscall/getpid.html>getpid</A></li> <li><A HREF=../syscall/open.html>open</A></li> <li><A HREF=../syscall/read.html>read</A></li> <li><A HREF=../syscall/write.html>write</A></li> <li><A HREF=../syscall/close.html>close</A></li> <li><A HREF=../syscall/remove.html>remove</A></li> <li><A HREF=../syscall/fork.html>fork</A></li> <li><A HREF=../syscall/execv.html>execv</A></li> <li><A HREF=../syscall/waitpid.html>waitpid</A></li> <li><A HREF=../syscall/_exit.html>_exit</A></li> </ul> </p> <p> <tt>multiexec</tt> should work once you have implemented the basic system calls. Exactly what the requirements are for handling large multiexec invocations is up to your course staff, although probably at a minimum your kernel shouldn't crash. </p> <p> Until you implement remove, which is typically not part of the basic system calls assignment, <tt>multiexec</tt> will not be able to clean up after itself. This is untidy but not a problem. </p> <h3>Bugs</h3> <p> <tt>multiexec</tt> has a compiled-in limit of 64 words in the argv array to be passed to its subprocesses. Also, there should be an easy way to pass a very large argv. In the meantime, perhaps try having <tt>multiexec</tt> run <A HREF=bigexec.html>bigexec</A>. </p> <h3>Restrictions</h3> <p> Be aware that until you do the VM assignment and replace dumbvm, running a lot of execs will run the system out of memory very rapidly. </p> </body> </html>