Running out of swap space?

[Kent Sandvik]

In article <1991Jan21.043607.22853 at servalan.uucp> rmtodd at servalan.uucp (Richard Todd) writes:
>ksand at Apple.COM (Kent Sandvik) writes:
>>In article <22762 at well.sf.ca.us> espen at well.sf.ca.us (Peter Espen) writes:
>
>>>	I have a 26K block partition on my A/UX 2.0 system. Why
>>>do I start getting out of swap space errors to the console 
>>>when a swap -l command shows that I have 13K blocks of  
>>>free swap space?
>
>>The swap space is used all the time, for instace a big process
>>(X Server or something similar) has to be swapped out, however
>>there's not enough space for the swap. In most cases one needs
>>to create more swap space, either on the same or another hard disk
>>drive. There is no such thing as virtual memory.
>
>That's all true, but it doesn't answer the question, namely, why the kernel
>says "WARNING: Swap Space Running Low" when you're *nowhere* *near* having
>the swap space full.  I have two swap partitions, each one 10 Meg.  Current
>total usage by all processes (as best I can tell, from a little VM monitor
>program I wrote), is around 13M.  Given an 8M Mac with about 5.5M free for 
>processes, that means that only about 7.5M of swap space should be in
>use, and indeed as we can see:
>37 servalan /usr/spool/uucp[5:34pm] % swap -l
>path              dev  swaplo blocks   free
>/dev/dsk/c0d0s1  24,1       0  20480  11792
>/dev/dsk/c2d0s1  26,1       0  20480  15216
>Noting that a "block" is 0.5K, this does indeed work out to about 7M of swap
>space in use out of a total of 20M.  So why does the kernel insist on giving
>warnings when less than half of my swap space is actually in use?  
>
>   In answer to the original poster: Ignore the warnings.  Trust me, when you
>really run out of swap space, you'll know it :-).  

Well, I can't answer much to that :-). Only that measuring swap space 
sizes in a multitasking environment is a tricky thing. One moment you
measure it's OK, meanwhile the scheduler is pushing for more space for
a swap. I've seen these messages with big processes running in the system,
and sure more swap space seems to help...

Regards,
Kent Sandvik


-- 
Kent Sandvik, Apple Computer Inc, Developer Technical Support
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