Messages in this thread |  | | Date | Mon, 25 Sep 2000 13:16:29 -0300 (BRST) | From | Rik van Riel <> | Subject | Re: the new VMt |
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On Mon, 25 Sep 2000, Alan Cox wrote:
> > > GFP_KERNEL has to be able to fail for 2.4. Otherwise you can get > > > everything jammed in kernel space waiting on GFP_KERNEL and if the > > > swapper cannot make space you die. > > > > if one can get everything jammed waiting for GFP_KERNEL, and not being > > able to deallocate anything, thats a VM or resource-limit bug. This > > situation is just 1% RAM away from the 'root cannot log in', situation. > > Unless Im missing something here think about this case > > 2 active processes, no swap > > #1 #2 > kmalloc 32K kmalloc 16K > OK OK > kmalloc 16K kmalloc 32K > block block > > so GFP_KERNEL has to be able to fail - it can wait for I/O in > some cases with care, but when we have no pages left something > has to give
The trick here is to: 1) keep some reserved pages around for PF_MEMALLOC tasks (we need this anyway) 2) set PF_MEMALLOC on the task you're killing for OOM, that way this task will either get the memory or fail (note that PF_MEMALLOC tasks don't wait)
This way the OOM-killed task will be able to exit quickly and the rest of the system will not get killed as a side effect.
regards,
Rik -- "What you're running that piece of shit Gnome?!?!" -- Miguel de Icaza, UKUUG 2000
http://www.conectiva.com/ http://www.surriel.com/
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