svn commit: r285387 - in head: lib/libc/sys share/man/man4 sys/conf sys/kern sys/sys sys/vm usr.bin usr.bin/numactl

[John Baldwin]

On Saturday, July 11, 2015 11:29:19 AM Alan Cox wrote:
> On 07/11/2015 10:21, Adrian Chadd wrote:
> >   * The VM doesn't handle unbalanced domains very well, and if you have an overly
> >     unbalanced memory setup whilst under high memory pressure, VM page allocation
> >     may fail leading to a kernel panic.  This was a problem in the past, but it's
> >     much more easily triggered now with these tools.
> >   
> 
> 
> For the record, no, it doesn't panic.  Both the first-touch scheme in
> 9.x and the round-robin scheme in 10.x fall back to allocating from a
> different domain until some page is found.

I got a panic (don't recall exactly which) with the 9.x version once
(albeit with that version backported to 8.x) where vm_page_alloc() returned
NULL when a caller did not expect it based on the global paging targets.
Unfortunately I no longer have access to the core (or any notes I might have
had from debugging it).  I don't recall why it didn't fall back to using a
page from another domain (especially since the 9.x version just prefers local,
doesn't require local).  Note that I only saw this once across hundreds of
machines running the 9.x version in production for 5 years or so.

-- 
John Baldwin