Re: Best way to pin a page in ext4?

On Tue, Sep 16, 2014 at 10:31:24PM -0500, Christoph Lameter wrote:

On Tue, 16 Sep 2014, Hugh Dickins wrote:

quoted

On the page migration issue: it's not quite as straightforward as
Christoph suggests.  He and I agree completely that mlocked pages
should be migratable, but some real-time-minded people disagree:
so normal compaction is still forbidden to migrate mlocked pages in
the vanilla kernel (though we in Google patch that prohibition out).
So pinning by refcount is no worse for compaction than mlocking,
in the vanilla kernel.

Note though that compaction is not the only mechanism that uses page
migration.

Agreed, and not all migration paths check for mlocked iirc. ISTR it is
very much possible for mlocked pages to get migrated in mainline.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>