Re: [PATCH 01 of 66] disable lumpy when compaction is enabled

Andrea Arcangeli
2010-11-09T21:32:11Z

On Tue, Nov 09, 2010 at 12:18:49PM +0900, KOSAKI Motohiro wrote:
> I'm talking very personal thing now. I'm usually testing both feature.
> Then, runtime switching makes my happy :-)
> However I don't know what are you and Mel talking and agree about this.
> So, If many developer prefer this approach, I don't oppose anymore.

Mel seem to still prefer I allow lumpy for hugetlbfs with a
__GFP_LUMPY specified only for hugetlbfs. But he measured compaction
is more reliable than lumpy at creating hugepages so he seems to be ok
with this too.

> But, I bet almost all distro choose CONFIG_COMPACTION=y. then, lumpy code
> will become nearly dead code. So, I like just kill than dead code. however
> it is also only my preference. ;)

Killing dead code is my preference too indeed. But then it's fine with
me to delete it only later. In short this is least intrusive
modification I could make to the VM that wouldn't than hang the system
when THP is selected because all pte young bits are ignored for >50%
of page reclaim invocations like lumpy requires.