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Why does it work?
Authored by: barrysharp on Apr 05, '02 01:45:50AM

That's really misses the point.

The swap feature is provided simply as 'poor man's memory'. This was when memory sizes were small and was expensive. Today memory isn't small nor is it expensive -- so load up with RAM to avoid your system from ever (well you can't avoid it altogether) swapping under the normal workload you place on your computer.

For example, I bought 1gig of memory about a year ago for $107 (2x 512MB modules for my iMac DV). My system hardly ever swaps out pages as reported by the top command. I run for weeks and top shows '(0)0 pagesouts' for me. This is with me using Virtual PC with Windows XP Professional loaded and using 256MB of memory.

If you can avoid swapping to the extent I have it matters not where the swapfile resides.

My advice to anyone is to load up with RAM and avoid swapping altogether. A system with 1 to 1.5 gig is very unlikely to promote pageouts for the average home computer user. Professional users might/could push the limits though.

Regards... Barry Sharp



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Why does it work?
Authored by: jzaw on Aug 21, '02 06:45:34AM

ive read with great interest your initial (long) vm explanations
and agree with and confirm observations of most of what youve said

but ...

can you speculate why my system (osx server 10.1.5) running just the standard file and web servers
and ftp craws to a damn halt when i try to temporaraly run a browser or email client on it

if i use top to see free ram and page outs ... after only a short time ive had 100,000's of page outs and the free ram sits at 9.5MB ish (ive got 768MB real ram installed)

i regularly have 13 swap files in my custom 1GB swap partition
though this figure does rise and fall

ive noticed that each week when the "weekly" script runs
my free ram rockets back to like 350-500MB free

i have done some lengthy observation and ive noticed that
the free ram is gradually eaten up as i tx files to and from the fileserver (via my ethernet lan)
free ram loss is on a 1:1 ratio with tx'd volumes
i can understand caching outgoing traffic (ready should it by chance be requested again)
but why would it need to cache and keep cached any incoming traffic?

if i had to describe the situation
its almost as if the system (kernel?) isnt giving up your "dirty cache" when a new (or old) application requires it

this threshold of approx 9.5MB doesnt seem to trigger any attempts to re acquire useable ram as free ram

the once the real ram is totally subscribed (after 24 hours or less) the system bogs down dramatically
(of course cos its paging in and out)

and whats worse is that this not only happens on OS X SERVER BUT ALSO ON OS X CLIENT (running filesharing)
(if the client has filesharing turned on and i access those files)
my client mac has 1GB of ram and is used mostly for graphics work
if i dont have the client mac do any filesharing then i dont get page outs
if i share files from the client ... i quickly get page outs and swapfile generation on that client
this is defo associated with the "server" action of a mac

tcp traffic seems to do exactly as you describe .... ie eat up the free ram with some sort of caching process
and then doesnt give it up

i have a small lan
2 macs
1 mac server
1 pc
linux box - router/firewall

the server is my graphics filestore
i run the webserver on the osx server to showcase my work to clients
(ie let them see the progress of the order of 100 -500 hits per week )
i run ftp from that same server to tx finished work to the client (once or twice a week)

the osx server mac is hardly taxed greatly ...
so the instruction to reduce its work load ... well i wouldnt know where to go with that?


any speculations as to why or how this is happening
any speculations as to what i can do to improve the system performance
i understand that a server is in the main not suposed to be used interactively on a regular basis
however as a lot of ppl dont have osx server and use a client os to share files this sort of slow down wouldnt be acceptable

and i do occasionally do that too

if you need any more info pls dont hesitate to ask
thanks in advance

Zaw



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Why does it work?
Authored by: gedboy on Oct 18, '04 06:54:11AM

jZaw I reckon I have a similar problem. I came across this via the Apple website btw.

G5 1.8 MHz DP with 1.5 GB of RAM running 10.3.5

My G5 has started crashing and needing a force restart in the last three weeks. I at first blamed Safari, then Eyetv but after a system reinstall and archive over the weekend the problem remains. Firefox has crashed it, as has iTunes but it could be any programme at this stage. Everyone is a suspect.

Looking at the Activity Monitor there are a few strange things. Generally I have about 1.1 GB free and almost no page outs. If I run something like Poisoned the giftd process takes 90% of the CPU and Inactive Memory zooms up to about 1 GB, leaving about 17 MB Free. Pageouts start climbing and the G5 hangs after abotu three minutes.

In Safari the same thing happens (except for the outrageous CPU usage) and eventually a hang is caused. Apart from the amazing speed with which Poisoned gobbles up CPU and RAM I can't exactly see a link in what's happening.

Currently Inactive RAM seems to be hovering on about 146 MB, going up AND down by about half a MB so this is cool but I only have Mail and Safari running beyond the normal system processes.

So the only thing I can see on my machine is that for some reason in some circumstances my Inactive RAM goes up until all my RAM is used then memory swapping starts until the system falls over. What is it that prevents Inactive RAM returning to Free RAM, or does that not happen anyway?

I will keep experimenting with combinations of programmes to see if there is an interaction between them that's doing it but this is driving me nuts. I even managed to crash via the Activity Monitor this morning.

In the good old days (last month) I could cheerfully have twenty programmes open and not be bothered.



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Why does it work?
Authored by: clith on Jan 18, '07 11:15:23AM

And yet, here I am in 2007 with a dual-dual-core cpu Mac Pro with 2 GB of RAM and my machine swaps madly sometimes, so now I am thinking of upgrading to 4 GB!

How are you guys in 2012 doing with your 16-core 8 GHz machines? I'm guessing 64 GB is good for you.. :-)



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