Date: Tue, 7 Feb 2012 09:49:33 +0000 From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: Doug Barton <dougb@FreeBSD.org> Cc: freebsd-jail@FreeBSD.org Subject: Re: Practical limit to number of jails on a given host? Message-ID: <5F01F653-A001-4EA1-9A99-F5C14CC39755@lists.zabbadoz.net> In-Reply-To: <4F30381E.2020100@FreeBSD.org> References: <4F30381E.2020100@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 6. Feb 2012, at 20:29 , Doug Barton wrote: > Howdy, >=20 > Thinking about implementing a poor-man's virtualization solution with > lots'o'jails, and wondering what people think about the practical = limits > of such a system. I realize that part of the answer is going to depend > on CPU and RAM, so let's assume for the sake of argument that the = answer > to that bit is, "Lots of both." >=20 > So first question is, is there some sort of hard-coded limit = somewhere? > If not, what is the largest number of jails that you've created > successfully/reliably on a system, and what are the specs for that = system? Yes, jails provide you 6 9s ... though that's not 99.9999% but 999999 is the maximum number of jails. And yes, I have started this many before = -- without processes or anything. It took a couple of days, due to some list handling, which could be optimized. You will find that once you get there, you'll have a syscall which never returns... You notice once the start loop slows down if you print a . every 100 or = 1000. The machine was a 4 or 8 core amd64 with 8G of memory. I think I had a slide in there: = http://www.bsdcan.org/2010/schedule/attachments/130_2010-bz-the-new-vvorld= .pdf I know if using vnets; you can get the 4k (or more) but I also have = reports that it may not scale. The other limit you'll run into is the number of PIDs. And eventually scheduling depending on what you want to do. > And finally, has anyone run into trouble with a large number of IP > addresses for the jails? ISTR that way back when, the IP addresses > associated with a particular interface were stored in a linked list, = so > as you added more you would start seeing O(N) slowdown on a lot of > network stuff in the kernel. Yeah, we still do list walks here and there. /bz --=20 Bjoern A. Zeeb You have to have visions! It does not matter how good you are. It matters what good you do!
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?5F01F653-A001-4EA1-9A99-F5C14CC39755>