Re: [squid-users] "Quadruple" memory usage with squid

On Wed, 2009-11-25 at 02:11 +0100, Henrik Nordstrom wrote:
> ons 2009-11-25 klockan 09:07 +1100 skrev Robert Collins:
> > On Tue, 2009-11-24 at 13:45 +0100, Henrik Nordstrom wrote:
> > > tis 2009-11-24 klockan 15:06 +1100 skrev Robert Collins:
> > >
> > > > http://www.netbsd.org/docs/kernel/vfork.html has some interesting notes
> > > > from the BSD world about this.
> > >
> > > vfork is fundamentally broken.
> >
> > Beyond the obvious (that it doesn't separate the memory out?)
>
> Undefined results if any of the following is used:
>
> - threads
> - signals
> - any form of output
> - pretty much any other syscall than an successful execve

In the 'vchild', yes. However I don't see why that would cause us
problems: in the child side of the vfork we would only be calling
execve / execvp - which will be fine.

> > > there is other alternatives coming, getting around the virtual memory
> > > issue when starting new processes.
> >
> > What are they called?
>
> Searching.. posix_spawn() and it's posix_spawnp() wrapper seems to be
> the one.

They use vfork (POSIX_SPAWN_USEVFORK) or fork internally. vfork has been
available for longer and should be trivial to drop in as an experiment,
whereas posix_spawn is still not widely available (and has precisely the
same issues for us).

-Rob