Re: [PATCH] oom_reaper: switch to struct list_head for reap queue

Ingo Molnar
2017-02-15T08:08:52Z

* Aleksa Sarai <asarai@suse.de> wrote:

> >>Rather than implementing an open addressing linked list structure
> >>ourselves, use the standard list_head structure to improve consistency
> >>with the rest of the kernel and reduce confusion.
> >>
> >>Cc: Michal Hocko <mhocko@suse.com>
> >>Cc: Oleg Nesterov <oleg@redhat.com>
> >>Signed-off-by: Aleksa Sarai <asarai@suse.de>
> >>---
> >> include/linux/sched.h | 6 +++++-
> >> kernel/fork.c | 4 ++++
> >> mm/oom_kill.c | 24 +++++++++++++-----------
> >> 3 files changed, 22 insertions(+), 12 deletions(-)
> >>
> >>diff --git a/include/linux/sched.h b/include/linux/sched.h
> >>index e93594b88130..d8bcd0f8c5fe 100644
> >>--- a/include/linux/sched.h
> >>+++ b/include/linux/sched.h
> >>@@ -1960,7 +1960,11 @@ struct task_struct {
> >> #endif
> >> int pagefault_disabled;
> >> #ifdef CONFIG_MMU
> >>- struct task_struct *oom_reaper_list;
> >>+ /*
> >>+ * List of threads that have to be reaped by OOM (rooted at
> >>+ * &oom_reaper_list in mm/oom_kill.c).
> >>+ */
> >>+ struct list_head oom_reaper_list;
> >
> >This is an extra pointer to task_struct and more lines of code to
> >accomplish the same thing. Why would we want to do that?
>
> I don't think it's more "actual" lines of code (I think the wrapping is
> inflating the line number count), but switching it means that it's more in
> line with other queues in the kernel (it took me a bit to figure out what
> was going on with oom_reaper_list beforehand).

It's still an extra pointer and extra generated code to do the same thing - a clear step backwards.

Thanks,

Ingo