Re: excessive swap-in time
- From: David Schwartz <davids@xxxxxxxxxxxxx>
- Date: Sun, 16 Mar 2008 18:05:28 -0700 (PDT)
On Mar 15, 7:53 pm, phil-news-nos...@xxxxxxxx wrote:
I guess I need to test a worst case scenario of how long it takes to read
in all of swap space when the pages are in random order.
Yeah. This is a case where the old "swap out the whole process" has an
advantage. As long as the whole process fits in memory, it's faster to
swap the whole thing in one fell swoop than to have to fault it in
page-by-page.
Another problem may be that if a process is idle for a long time and
then becomes active, many of its pages may be the least recently used
pages in the system. So when it starts causing a swap in, it may well
swap itself out to get the pages in, resulting in an amusing musical
chairs fiasco.
You can think of obvious ways to tweak this to make this one case
perform better, but you can think of cases that are made worse by
those same tweaks.
Don't expect much help -- most programmers are working on efficient
ways to use more memory rather than better ways to handle low memory
situations. (Many typical machines now have 4GB-8GB and working sets
that seldom exceed 1.5GB.)
DS
.
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