Date: Sun, 14 May 2006 13:05:15 -0500 From: Andrew <andrew.chace@gmail.com> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-questions@freebsd.org Subject: Re: VM and jailed processes Message-ID: <1147629915.10075.27.camel@LatitudeFC5.network> In-Reply-To: <44671864.2020001@mac.com> References: <1147578337.10075.12.camel@LatitudeFC5.network> <44671864.2020001@mac.com>
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On Sun, 2006-05-14 at 07:45 -0400, Chuck Swiger wrote: > Andrew wrote: > > It's my understanding that if there is more than one instance of a > > specific application running, then portions of the code are shared in > > memory. I would assume that would apply to dynamically linked > > applications as well; i.e. if two different applications are linked > > against the same library, the given code exists in only one location in > > memory. Is this correct? > > Yes. The details are more complicated, but the portion of an executable > which contains code and does not change can be shared between many > processes from only one copy in physical RAM, and likewise for shared > libraries loaded by dynamic or runtime linking. > > > The second portion of my question is, how does this apply to jailed > > processes? Looking through the architecture handbook, I did not see any > > references to VM, which leads me to believe that the standard rules > > apply to jails as well. So, for instance, if I was to provide a hosting > > service with numerous instances of Apache running in individual jails, > > could I assume that base memory usage (ie idle, not serving requests) > > would increase at a roughly linear rate. > > > > The same thing applies to jails, and the static portions of apache/httpd > will only appear once in RAM, however, you are going to see roughly > linear increase in memory usage depending on the number of children > running, because there's anywhere from 1MB to 25MB or so of dynamic > memory being used per httpd which is specific to that process, depending > on which modules you're using and whether you are loading perl or PHP > scripts.... > Hi Chuck, Thank you for the clarifications. It seems as though this will work quite well; the hosting setup, that is. I would have to assume that this has been done many times before, but it's always fun to have an idea pan out the way that you expected it to! -Andrew
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