Re: [patch] mm, thp: always direct reclaim for MADV_HUGEPAGE even when deferred

From: Michal Hocko
Date: Fri Dec 30 2016 - 07:59:08 EST

On Fri 30-12-16 12:36:20, Mel Gorman wrote:
> I'll neither ack nor nak this patch. However, I would much prefer an
> additional option be added to sysfs called defer-fault that would avoid
> all fault-based stalls but still potentially stall for MADV_HUGEPAGE.

Would you consider changing the semantic of defer=madvise to invoke
KSWAPD for !madvised vmas as acceptable. It would be a change in
semantic but I am wondering what would be a risk and potential
regression space.

Also I am planning to send a pro-active compaction based on a
"watermark" as an LSF/MM topic proposal. I suspect that no additional
thp specific tunable will be needed if we have a proper compaction
watermark tunable.
Michal Hocko