Date: Tue, 23 Jun 2009 16:56:26 -0400 From: Michael Scheidell <scheidell@secnap.net> To: Tom Haapanen <tomh@motorsport.com> Cc: freebsd-jail@freebsd.org Subject: Re: Memory usage across multiple jails Message-ID: <4A41417A.9080805@secnap.net> In-Reply-To: <0c1201c9f43e$166c8450$43458cf0$@com> References: <0c1201c9f43e$166c8450$43458cf0$@com>
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Tom Haapanen wrote: > I have been using FreeBSD (and other forms of *BSD) a long time, but I'm new > to the world of jails. I have been doing reading on them, but there is one > question I have not been able to find an answer to, and that's the > efficiency of memory usage when using multiple jails on a single system. > > > > With "conventional" virtual machines (VMware, Virtual Server et al), > essentially each VM is opaque to the host OS, and thus has to be allocated X > MB of memory, which that VM then manages internally. > > > im been expermenting with some of this disk cache (malloc, etc) is shared. if httpd is different in each jail (even if its the same), then example: jail 1 has 4 httpd's running, one copy (of binary) will be in memory, 4 copies of data structure jail 2 has 10 httpd's running, its got one (more) copy of binary, and 10 copies of data structure. HOWEVER if you nullmount /usr/local/bin ../sbin .../libexec ../lib then you CAN share the one httpd binary. other issue is static libs. in /usr/lib these aren't likely shares, as when you build the jail, you made COPIES of /usr/lib so, nullfs mount /usr/lib /usr/bin /usr/sbin /sbin, /usr/libexec, maybe you can get the most out of it. (but, 6 freebsd jails use a heck of a lot ram than 6 vmware images) > However, since jails are based on the FreeBSD kernel, and both host and > guest OSs are identical, I am wondering whether there are any comparative > efficiencies in memory utilization. Will the jails share the disk cache, > for example, or does each jail allocate its own? Will other kernel > structures (and code!) be shared across jails, or allocated multiple times? > And what about userland applications, like httpd, for example? (I suspect > userland would not be able to benefit, but that's just a guess.) > > > > Thanks for any insight into this ... > > > > Tom > > _______________________________________________ > freebsd-jail@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-jail > To unsubscribe, send any mail to "freebsd-jail-unsubscribe@freebsd.org" > -- Michael Scheidell, CTO Phone: 561-999-5000, x 1259 > *| *SECNAP Network Security Corporation * Certified SNORT Integrator * 2008-9 Hot Company Award Winner, World Executive Alliance * Five-Star Partner Program 2009, VARBusiness * Best Anti-Spam Product 2008, Network Products Guide * King of Spam Filters, SC Magazine 2008 _________________________________________________________________________ This email has been scanned and certified safe by SpammerTrap(r). For Information please see http://www.secnap.com/products/spammertrap/ _________________________________________________________________________
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