Simple swap question

FreeBSD freebsd at
Thu Dec 18 20:11:46 UTC 2008

Daniel Bye a écrit :
> On Thu, Dec 18, 2008 at 12:02:06PM -0500, FreeBSD wrote:
>> Daniel Bye a ?crit :
>>> On Thu, Dec 18, 2008 at 10:28:18AM -0600, Kirk Strauser wrote:
>>>> On Thursday 18 December 2008 09:16:10 FreeBSD wrote:
>>>>> Hi everyone,
>>>>> I have a FreeBSD 7.0-Release server that started to swap after an error
>>>>> in a shell script (process spawning competition ;-) ). I killed the
>>>>> shell and the RAM is now OK. The problem is that the swap is still used.
>>>>> How can I "reset" the swap?
>>>> You don't.  The system will handle it for you, I promise.  :-)
>>> And very well, too.
>>> You can prompt it to move pages back into RAM if you start using a swapped-
>>> out process again - say, for example, a quiescent word processor had been
>>> swapped out, you could get it back by raising it and starting to type.
>>> But as Kirk said, there really is no need. It's one of the kernel's many
>>> jobs, and I'm inclined to leave it get on with it!
>>> Dan
>> Thanks for your answer. I'm asking here because it's been several days 
>> and there is still used swap for data that should never be used anymore. 
>> If the kernel wants to keep it, why not move it to RAM now that there is 
>> some free?
> Because it has swapped out an entire process, which hasn't subsequently
> been woken up again. It's you that says the data are never going to be
> needed again - the kernel doesn't know that, so keeps the pages there in
> swap until you either reawaken the process, or kill it, at which point
> the swap space they occupied will be freed up.
> You can see which processes are swapped out in top - the process name is
> in parentheses. If it is irking you sufficiently, you can kill the
> processes and reclaim your swap ;-)
> Dan

I can't see any process within parentheses in top... I also looked at 
the -f option of ps but the process that caused the swapping are not listed.

Thanks for helping me clarify this.


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