On 02/11/2011 06:26 AM, Torsten Förtsch wrote:
> Now, if an administrator turns off swapping (swapoff /dev/...) the part of
> notpresent that has been there becomes present. So, we can expect shared to
> grow considerably. unshared will shrink by the same amount.
>
> But if an administrator turns off swapping now a part of notpresent will be
> added to unshared. unshared may suddenly jump over the limit in all apache
> children.
Hey Torsten. First of all, wow, thank you for this awesome write-up.
That was probably the best overview of copy-on-write and page types I've
ever read.
I think that if an administrator turns off the swap, they would in fact
*want* ASL to behave such that it killed httpds that were taking up too
much physical RAM, even if that happened suddenly. The space for mapping
pages to has suddenly decreased drastically, so it makes sense to
suddenly be much more aggressive about killing processes.
> There are a few other status fields that can be possibly used:
>
> - "Swap" in /proc/$PID/smaps
> don't know for sure what that means but sounds good. Need to inspect the
> kernel code
Hmm, if that does actually count the size of mapped swap pages, then we
could possibly do rss + swap as the "size".
-Max
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