weening@Gang-of-Four.Stanford.EDU (Joe Weening) (03/10/90)
When I run "mon -m", the bottom line on the screen shows the current amount of free memory. In our system, with 48MB of physical memory, this number never seems to go much below 5MB. I'd like to make it much closer to zero, so that user processes can use more of the available memory. Is there a way to do this? -- Joe Weening Computer Science Dept. weening@Gang-of-Four.Stanford.EDU Stanford University
collins@osf.org (Jeff Collins) (03/10/90)
In article <1990Mar9.174826.11922@Neon.Stanford.EDU>, weening@Gang-of-Four.Stanford.EDU (Joe Weening) writes: > When I run "mon -m", the bottom line on the screen shows the current > amount of free memory. In our system, with 48MB of physical memory, > this number never seems to go much below 5MB. I'd like to make it > much closer to zero, so that user processes can use more of the > available memory. Is there a way to do this? > > -- > Joe Weening Computer Science Dept. > weening@Gang-of-Four.Stanford.EDU Stanford University That number indicates the amount of free memory. If there is any free memory and it is needed by a program it will be allocated. In other words, if the memory demand on you system was sufficient, then that number would go down. Your next question might be "does my kernel start paging to keep that number at 5MB or higher?" The answer is no. The kernel is very smart about how it allocates physical memory and when it starts paging. Be satisfied with the fact that your user communitee is not demanding more than, on average, 43MB of physical memory. If the user communitee needed more than this it would be allocated, and the number would go below 5MB free. Jeffery A. Collins Phone: (617) 621-8958 Open Software Foundation FAX: (617) 225-2782 11 Cambridge Center Email: collins@osf.org Cambridge MA 02142 uunet!osf.org!collins
weening@Gang-of-Four.Stanford.EDU (Joe Weening) (03/10/90)
In article <4843@paperboy.OSF.ORG> collins@osf.org (Jeff Collins) writes:
That number indicates the amount of free memory. If there is any free
memory and it is needed by a program it will be allocated. In other words,
if the memory demand on you system was sufficient, then that number
would go down. Your next question might be "does my kernel start paging
to keep that number at 5MB or higher?" The answer is no. The kernel is
very smart about how it allocates physical memory and when it starts
paging.
Saying that the kernel is "very smart" doesn't convince me at all.
Perhaps you could describe the algorithms used by the Alliant kernel.
It certainly doesn't always act reasonably for us.
Be satisfied with the fact that your user communitee is not
demanding more than, on average, 43MB of physical memory.
Our user community (not "communitee") demands quite a bit more than
43MB of physical memory. Actually our user processes demand virtual
memory, and the kernel decides how to allocate physical memory. But
we're often running several Lisp processes, each of which would get a
running set size of over 20MB if it was running alone. This along
with the xterm, emacs, csh, etc. processes drives the usage way above
our actual physical memory.
If the user communitee needed more than this it would be allocated,
and the number would go below 5MB free.
Sorry, you're making assumptions about our environment and about what
is happening that are simply not correct.
Our free memory sometimes does go below 5MB, but never very close to
zero. The memory usage of large processes often causes swapping (not
paging) of other processes, which then have to fight their way back
into memory when they become active (like responding to a keystroke).
This happens while there is plenty of free memory available.
--
Joe Weening Computer Science Dept.
weening@Gang-of-Four.Stanford.EDU Stanford University