OSv has already a concept of module but I wonder if its core can be made 
modular as well. For example there could be something like osv.base, osv.io 
(osv.io.read, osv.io.write, etc), osv.net, etc  I do not know enough it it 
makes sense but even POSIX systems calls can be grouped into modules and 
then pulled like lego blocks depending on what one needs. I am looking at 
the modularity of Java 9 runtime (http://openjdk.java.net/jeps/220) which I 
am trying to draw an parallel to. 

Would it be possible? Is it a big effort? 

On Sunday, September 18, 2016 at 12:08:22 PM UTC-4, Nadav Har'El wrote:
> On Fri, Sep 16, 2016 at 3:28 AM, Ian Eyberg <i...@deferpanic.com 
> <javascript:>> wrote:
> Hi All:
>>   I gave a presentation last night at the ACCU meetup on the 'Current 
>> State of C++ Unikernels'. Dor happened to be around and mentioned that this 
>> list might be interested in seeing the slides I was presenting so here they 
>> are: 
>> https://speakerdeck.com/eyberg/the-current-state-of-c-plus-plus-unikernels 
>> - I don't know how many people showed up but I'm guessing there was 
>> somewhere around 40-50. Also - if you're in the Bay Area we have regular 
>> unikernel meetups and definitely are looking for more speakers - 
>> http://www.meetup.com/San-Francisco-Unikernels/ .
>> - Ian
> Thanks. Very interesting.
> It seems that one of the places that OSv is outdone by the other 
> unikernels you surveyed is in its size.
> This is partly to blame for the current approach of OSv to always include 
> the entire kitchen sink - the entire Posix, Linux, etc., file system, 
> networking, etc. - even if the application doesn't really needs them. 
> Unlike Linux we don't have a huge amount of irrelevant stuff (like floppy 
> disk drivers), but some applications may nonetheless find whole chunks of 
> OSv to be irrelevant for them, and may want a smaller OSv without them.
> For example, we currently support building OSv without a permanent 
> filesystem (only a ram drive) so it compiles without ZFS in the kernel, and 
> without ZFS-related tools, which lowers both the image size and memory use. 
> If you build the silly game "rogue" without a permanent filesystem, 
> ""scripts/build image=rogue fs=ramfs", the resulting image size is only 6.6 
> MB.
> In your slide you listed OSv's "size" as 29 MB. I don't know if this 
> refers to to the image size (which, as I said above, can be much lower) or 
> to the memory size. OSv's memory size is also "excessive" (in Super Mario 
> standards) because of some silly compromises we took, such as:
>  1. We have a silly lower limit on the memory we use because of reasons 
> explained in https://github.com/cloudius-systems/osv/issues/195. This 
> lower limit can be made configurable - currently it is set to about 25 MB.
>  2. All the kernel code is loaded into memory, so the more non-useful 
> stuff we compile in, the more memory we need.
>  3. Moreover, some areas of the code use too much memory - for example the 
> ZFS system starting a bunch of threads (see 
> https://github.com/cloudius-systems/osv/issues/247) and also a generous 
> cache, some code uses generous amounts of buffers, etc.
>  4. pthread stacks are allocated in advance: see 
> https://github.com/cloudius-systems/osv/issues/143
> If anyone is interested to work on these issues, or other directions of 
> making OSv smaller, I'd be happy :-)

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