Re: [RFC][PATCH 2/9] deadlock prevention core

From: Andrew Morton
Date: Fri Aug 18 2006 - 22:49:14 EST

On Fri, 18 Aug 2006 16:44:01 -0700
Daniel Phillips <phillips@xxxxxxxxxx> wrote:

> handwaving

- The mmap(MAP_SHARED)-the-whole-world scenario should be fixed by
mm-tracking-shared-dirty-pages.patch. Please test it and if you are
still able to demonstrate deadlocks, describe how, and why they
are occurring.

- We expect that the lots-of-dirty-anon-memory-over-swap-over-network
scenario might still cause deadlocks.

I assert that this can be solved by putting swap on local disks. Peter
asserts that this isn't acceptable due to disk unreliability. I point
out that local disk reliability can be increased via MD, all goes quiet.

A good exposition which helps us to understand whether and why a
significant proportion of the target user base still wishes to do
swap-over-network would be useful.

- Assuming that exposition is convincing, I would ask that you determine
at what level of /proc/sys/vm/min_free_kbytes the swap-over-network
deadlock is no longer demonstrable.

If there are any remaining demonstrable deadlock scenarios, please describe
how they were created and, if possible, perform some analysis of them for
us. sysrq-T and sysrq-M traces would be helpful.

Once we have this information in hand, we will be in a better position to
work out how to solve these problems.

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