Subject: Re: emulation speeds?
To: Frank van der Linden <email@example.com>
From: Scott Bartram <scottb@iis.NET>
Date: 08/17/1995 10:21:56
> Quoting Robert Dobbs,
> > I run some emulated binaries (BSDI and Linux), but nothing that is
> > really hefty. What sort of cost is involved in running these?
> > Do they run very close to native system speed?
> For Linux binaries, there are 2 issues:
> 1. Loading the binary might take longer, because the Linux shared libs
> may have to be loaded (if this is the first Linux binary you run). For
> NetBSD binaries you won't really notice this, because the shared
> libs have been mapped sometime during system startup when the first
> shared binary was run. Also some Linux binaries can't be demand paged
> 2. There is a little overhead in some system calls, some structure
> conversions and copyin/copyout going on. However, this doesn't affect
> some of the heavily used system calls, like read(2) or write(2).
> For BSDI binaries, point 2 does not apply. I am not sure if they have
> shared libraries yet (does 2.0 have them?).
2.0 has "fixed address" shared libraries (yuck!). Yet more emulation
code to be written :-(