Re: [PATCH V5] Allow compaction of unevictable pages

[Eric B Munson <emunson@akamai.com>]

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On Fri, 13 Mar 2015, Rik van Riel wrote:

> On 03/13/2015 01:26 PM, Eric B Munson wrote:
> 
> > --- a/mm/compaction.c
> > +++ b/mm/compaction.c
> > @@ -1046,6 +1046,8 @@ typedef enum {
> >  	ISOLATE_SUCCESS,	/* Pages isolated, migrate */
> >  } isolate_migrate_t;
> >  
> > +int sysctl_compact_unevictable;
> > +
> >  /*
> >   * Isolate all pages that can be migrated from the first suitable block,
> >   * starting at the block pointed to by the migrate scanner pfn within
> 
> I suspect that the use cases where users absolutely do not want
> unevictable pages migrated are special cases, and it may make
> sense to enable sysctl_compact_unevictable by default.

Given that sysctl_compact_unevictable=0 is the way the kernel behaves
now and the push back against always enabling compaction on unevictable
pages, I left the default to be the behavior as it is today.  I agree
that this is likely the minority case, but I'd really like Peter Z or
someone else from real time to say that they are okay with the default
changing.

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