From: SeongJae Park <sjpark@xxxxxxxxx> Hello Matthew, On Sat, 12 Jun 2021 01:07:14 +0100 "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> wrote: > In discussion with other MM developers around how idle page tracking > should be fixed for transparent huge pages, several expressed the opinion > that it should be removed as it is inefficient at accomplishing the > job that it is supposed to, and we have better mechanisms (eg uffd) for > accomplishing the same goals these days. I think the THP case[1] is an intended behavior[2]. Could you please share a link to the discussion or a detailed summary if possible? > > Mark the feature as BROKEN for now and we can remove it entirely in a > few months if nobody complains. It is not enabled by Android, ChromeOS, > Debian, Fedora or SUSE. Red Hat enabled it with RHEL-8.1 and UEK followed > suit, but I have been unable to find why RHEL enabled it. Amazon Linux is also using it[3], for DAMON[4]. In detail, DAMON doesn't use Idle Page Tracking but PG_Idle in kernel space, to avoid interfering the reclaim logic[5]. So, I'm ok with removing the Idle Page Tracking user space interface, but gonna be opposed to removing PG_Idle. Nevertheless, the interference is not a real problem to DAMON, as DAMON is aimed to provide just a reasonable quality of the monitoring, rather than strict correctness. Hence, if people think the interference is also not a problem for the reclaim logic (after all, it does nothing unless sysadmin manually turns it on in runtime, and can be turned off at anytime), I would simply update DAMON code to don't use PG_Idle, add warnings in the doc, and wouldn't be opposed to this change. But, if not, I think this change will be a big problem to us. If the problem is a lack of dedicated maintainer for Idle Page Tracking or PG_Idle, I can volunteer. [1] https://lore.kernel.org/linux-mm/YMGKVmt8trMJ9kOP@xxxxxxxxxxxxxxxxxxxx/ [2] https://lore.kernel.org/linux-mm/20210614081610.16123-1-sjpark@xxxxxxxxx/ [3] https://github.com/amazonlinux/linux/blob/amazon-5.10.y/master/mm/damon/Kconfig#L19 [4] https://lore.kernel.org/linux-mm/20210520075629.4332-1-sj38.park@xxxxxxxxx/ [5] https://lore.kernel.org/linux-mm/20210525154427.30921-1-sjpark@xxxxxxxxx/ Thanks, SeongJae Park [...]
