On Sun, Feb 18, 2018 at 04:47:55PM +0000, robert.m.har...@oracle.com wrote:
> From: "Robert M. Harris" <robert.m.har...@oracle.com>
> __fragmentation_index() calculates a value used to determine whether
> compaction should be favoured over page reclaim in the event of allocation
> failure.  The calculation itself is opaque and, on inspection, does not
> match its existing description.  The function purports to return a value
> between 0 and 1000, representing units of 1/1000.  Barring the case of a
> pathological shortfall of memory, the lower bound is instead 500.  This is
> significant because it is the default value of sysctl_extfrag_threshold,
> i.e. the value below which compaction should be avoided in favour of page
> reclaim for costly pages.
> This patch implements and documents a modified version of the original
> expression that returns a value in the range 0 <= index < 1000.  It amends
> the default value of sysctl_extfrag_threshold to preserve the existing
> behaviour.
> Signed-off-by: Robert M. Harris <robert.m.har...@oracle.com>

You have to update sysctl_extfrag_threshold as well for the new bounds.
It effectively makes it a no-op but it was a no-op already and adjusting
that default should be supported by data indicating it's safe.

Mel Gorman
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Reply via email to