Path: utzoo!utgpu!attcan!sobmips!roe
From: roe@sobmips.UUCP (r.peterson)
Newsgroups: comp.unix.i386
Subject: Re: Help!  Altos 5.3.1 fork is failing!
Message-ID: <1989Oct21.014907.29202@sobmips.UUCP>
Date: 21 Oct 89 01:49:07 GMT
References: <3684@altos86.Altos.COM>
Organization: Sobeco Group - Montreal, Canada
Lines: 37

From article <3684@altos86.Altos.COM>, by jerry@altos86.Altos.COM (Jerry Gardner):
> In article <506@oglvee.UUCP> jr@oglvee.UUCP (Jim Rosenberg) writes:
> 
> Getpages is an internal kernel routine that allocates contiguous pages of
> kernel virtual memory.  It's not called by the paging daemon, but rather to
> allocate or grow regions, among other things.
> 
>>Is there a tunable parameter that will rescue me here?  
>>
> 
> Not really.  You really are running out of swap space.  Even though
> "swap -l" may  show plenty of swap space remaining, it is misleading.
> 
> UNIX allocates swap space for the entire .data and .bss regions whenever
> a process is exec'ed.  Even though swap -l shows plenty of swap space 
> available, most of the swap space is allocated to processes, which, although
> they may not currently be swapped out, still tie up the swap space.
> 
> Your best solution: get more RAM.

Not true.  While unix does CHECK FOR available swap space for the entire .data
and .bss regions whilst fork()ing, it does NOT necessarily USE that
space.

Simply increasing available swap space will solve the problem.  You will
not begin to thrash, since demand paging is still in effect.

The BSD file systems simply want to know that, if necessary, there is
enough swap space to swap.

We saw the same problem on our MIPS systems, and adding another swap
partition solved the problem - with no noticable (sar, vsar, etc)
performance degredation.

-- 
					Roe Peterson
					{attcan,mcgill-vision,telly}!sobeco!roe