Hi,
> Can't we use something like the L4's small address space concept on Mach?
> There is an area on top of the linear address space which is protected by
> segmentation. It is common for
> all tasks. Some small tasks (a few megs of memory space) are mapped there.
> When the control is transferred
> to one of these tasks the kernel adjusts the segmentation and lets the task
> run without any context switch.
There is nothing stopping us from doing just that. However, you must keep
in mind that the hurd is a multi server operating system and by design,
all parts are replaceable. How does the operating system, decide what
to map into the space?
In ia32, we have a 4 gigabyte address space. Big right? Hardly. Have you
ever considered why you can only have ~1 gigabyte partitions? Currently,
the implementation maps the entire partition as a continuous chunk into
the virtual address space. Try taking a look at some of the other processes
to. None are terrible small. Bash takes up nearly 150 megs on my system.
When 64 bit systems become popular, this will not be as much of a problem.
Then, some funky things can be done with the page tables, however, until then,
very little can conceivably be mapped across all address spaces.
Here is a dump from my system, note that SZ is the size of the process's
address space.
neal@hurd:~$ ps -A -F vmem
PID STAT SZ RSS %CPU %MEM COMMAND
2 D<p 219M 6.16M 0.0 3.2 /boot/gnumach.gz root=hd0s3
4 So 1.05G 4.47M 0.0 2.3 /hurd/ext2fs.static --bootflags=-x --host-priv
42 So 1.06G 3.46M 0.0 1.8 hurd/ext2fs /dev/hd0s1
38 So 131M 2.03M 0.0 1.1 /hurd/pfinet -i eth0 -a 129.63.200.245 -g 129.
445 So 130M 1.54M 0.0 0.8 /hurd/pfinet -i eth0 -a 192.168.0.3 -g 192.168
36 Sslo 146M 1.45M 0.0 0.8 -bash
2883 Sslow 146M 1.44M 0.0 0.8 -bash
449 So 130M 1.33M 0.0 0.7 /hurd/ftpfs ftp.debian.org:/debian/dists/unsta
7 Sslow 146M 1.25M 0.0 0.7 /bin/sh /libexec/runsystem
0 R<mo 130M 1.23M 0.0 0.6 /hurd/proc
40 So 130M 1.19M 0.0 0.6 /hurd/password
2882 So 146M 1.15M 0.0 0.6 in.telnetd
158 So 130M 1.13M 0.2 0.6 /hurd/term /dev/ptyp0 pty-master /dev/ttyp0
448 So 1.04G 1.12M 0.0 0.6 /hurd/ext2fs /dev/hd0s2
5 So 130M 1.11M 0.0 0.6 /hurd/exec
etc.
-Neal
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Neal Walfield [EMAIL PROTECTED]
UMass Lowell - Fox 1512 Phone: 978-934-5347
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