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Re: netbsd-5 deadlocks when memory is low

Emmanuel Dreyfus <> wrote:

[using mlockall(2) to prevent userland filesystem to be swaped out]
> It seemed to work, but after intensive testing I still see deadlocks,
> and a printf added in uvm_swapout() shows that perfused still gets
> swaped out despite the mlockall call. Is that a bug?
> This is on netbsd-5. 

I had a look at src/sys/uvm/uvm_glue.c changes bewteen netbsd-5 and
-current. Revision 1.140-1.141 is interesting: netbsd-5 has a swappable
u-area, and the change drops that "feature" to fix issues.

The problem is documented in kern/38828

Is it possible that mlockall() fail to wire the u-areas, leading to the
problem again?

The changeset is huge, but it does not only make the u-area unswappable.
Is it reasonable to try to isolate that change and backport to netbsd-5?

Emmanuel Dreyfus

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