Re: [RFC][PATCH 1/1] Expose per-node reclaim and migration to userspace

Christoph Lameter
2006-11-30T04:13:44Z

On Wed, 29 Nov 2006, Paul Menage wrote:

> Quite possibly - I don't have a strong feeling for exactly where the
> code should go. There's existing code (sys_migrate_pages) that uses
> the migration mechanism that's in mm/mempolicy.c rather than
> migrate.c, and this was a pretty simple function to write.

Plus there is another mechanism in mm/migrate.c that also uses the
migration mechanism.

> We don't need to expose the raw "priority" value, but it would be
> really nice for user space to be able to specify how hard the kernel
> should try to free some memory.

Would it not be sufficient to specify that in the number of attempts like
already provided by the page migration scheme?

> Then each job can specify a "reclaim pressure", i.e. how much
> back-pressure should be applied to its allocated memory, so you can
> get a good idea of how much memory the job is really using for a given
> level of performance. High reclaim pressure results in a smaller
> working set but possibly more paging in from disk; low reclaim
> pressure uses more memory but gets higher performance.

Reclaim? I thought you wanted to migrate memory of a node?