How low can you go, with RAM?

Is it possible to boot with only 48M of RAM in a DragonFly system?  Probably not.  128M would be better.  I usually talk about the lower memory limit for Hammer, since it’s so relatively low for a snapshotting file system, but the converse applies here.  128M is probably the comfortable lower limit, though it’s pretty hard to find a system that would limit you that way without doing it on purpose.  128M sticks of RAM are practically disposable these days, really.

10 Replies to “How low can you go, with RAM?”

  1. 128MB is insufficient for an x86_64 build, I believe, you need more like 160-192MB for that (at least).

    Also, I challenge you to actually find a new 128MB stick of RAM for sale. With a new 2GB stick of RAM going for as low as $12* USD and x86 computers older than approx. 3-4 years being basically give-away items, all of which have at least 512MB-1GB memory at this point. It is a waste of developer effort to attempt to maintain functionality on such antiquated hardware.


  2. My P150 has 128 MB of RAM, and I can’t fit any more into it, you insensitive clod!

    (I also have a P133 which I upgraded to 24 MB, from 16 MB)

  3. We need to behave well on low mem, and we have VM, so I guess dfly *must* behave well on small mem systems. In the past dfly has worked quite well on scrap HW; I used 128MB for my nfs server for a long time, it worked very well, also after HAMMER entered. I guess a 64 MB and maybe even 48 and 32 MB system will run UFS quite fine, will test. On a small mem system you will not need to build world or kernel.

  4. I did some small test, setting hw.physmem in loader.conf: going down 40M works ok, but with 32M system boots without problem, but small job, like man page formatting causes heavy paging. This was not a totally stripped down system, just no HAMMER or X use.

  5. aesoppatch, from the perspective of a developer — those who have expectations of the system working on such antiquated hardware are the insensitive ones.

    thomas, behaving well with say, 256mb of memory is something different entirely than working on a 16 or 32mb machine.

    The absolute smallest piece of hardware I know about that you can even buy nowadays (that is x86, which is all we support) has 64MB. For a system of such size, the only reasonable way to approach deployment to it, in my opinion, is to have a larger/faster host system to build a kernel and etc. for it on. You should be able to save several non-pageable megabytes of RAM with a custom kernel build, that could be 5% on a 64mb machine, which is non-trivial.

  6. I just installed Dragonfly on an old Toshiba Lifebook 790tx with 56 megs of ram and a 4GB hard drive. I used the USF option, with the suggested partition layout.

  7. sjg: I fully agree on you comment (as usual :)
    My comment is that on current dfly release 48MB seems to work nice running smaller programs. For more demanding programs it is a no-go, it will die in paging or other resource shortage.
    Seems like preformatted man pages had its reason when systems had mem like this (or far lower :)

  8. Thomas, yeah, I think it’s great that we can and do work on a 48MB machine. To be perfectly honest if a person actually cared to, I am sure the kernel could be fairly easily pared down to support a 16MB installation, maybe less. But it simply isn’t worth it for us to maintain (which means testing) support for such systems, because there is not a _reasonable_ use-case. Installing onto (original) p5-class hardware is probably not a reasonable use-case, whereas a 586-class Soekris probably is, but those all come with at least 64MB.

    If there is really interest in this (low-memory installs of DragonFly), then it would be great if someone would write a “low-memory tuning guide” for the website, in truth it would probably be helpful for anyone with less than as much as 512MB-1GB. Most of our kernel design decisions are based around the idea of a “modern” desktop/server, which means we reasonably expect at least 512MB-1GB or more. During the process one might discover some easy changes that we can make (meaning they don’t impede long-term maintenance) that could make the OS work better on low-memory systems out of the box.

  9. I’ve been running a P1 64MB FreeBSD 7.3 as a fileserver for 2 years now, have to look into DragonFlyBSD

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