Re: Overcommitable memory??

From: Marco Colombo (
Date: Wed Mar 22 2000 - 05:42:34 EST

On Tue, 21 Mar 2000, James Sutherland wrote:

> Giving apps more information about memory usage would certainly help.
> If Squid could just be told "use 50% of the free memory as a cache" it
> would make life a lot simpler :-)
> Ideally, you would get a trappable signal which says "We're getting
> short on memory, can you cut down your usage?" Then your well-behaved
> app would trim itself a bit, solving the problem without killing
> anything.

This "ideal" solution will have to cope with *all* processes requesting
at the same time their signal handlers + garbages collectors (which
are not part of their working-sets) being paged-in to be executed.
This will increase pressure on the mm subsystem a lot. A lot of RAM should be
freed to allow this sudden change in the working set of all processes.
Garbage collectors on "big" processes are likely to touch most of their
data pages in search of "victims" to be garbaged.
Much like when you're short of CPU cycles to ask every process to
*recompute* its CPU needs.
 "Don't panic, don't panic; OK, panic!" B-)

> James.


      ____/  ____/   /
     /      /       /			Marco Colombo
    ___/  ___  /   /		      Technical Manager
   /          /   /			 ESI s.r.l.
 _____/ _____/  _/

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to Please read the FAQ at

This archive was generated by hypermail 2b29 : Thu Mar 23 2000 - 21:00:35 EST