On Thu 12-01-17 14:46:34, David Rientjes wrote:
> When memory.move_charge_at_immigrate is enabled and precharges are
> depleted during move, mem_cgroup_move_charge_pte_range() will attempt to
> increase the size of the precharge.
>
> This can be allowed to do reclaim, but should not call the oom killer to
> oom kill a process. It's better to fail the attach rather than oom kill
> a process attached to the memcg hierarchy.
This is not the case though since 3812c8c8f395 ("mm: memcg: do not trap
chargers with full callstack on OOM") - 3.12. Only the page fault path
is allowed to trigger the oom killer.
> Prevent precharges from ever looping by setting __GFP_NORETRY. This was
> probably the intention of the GFP_KERNEL & ~__GFP_NORETRY, which is
> pointless as written.
>
> Fixes: 0029e19ebf84 ("mm: memcontrol: remove explicit OOM parameter in charge path")
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Without the note about the oom killer you can add
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> mm/memcontrol.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4353,9 +4353,12 @@ static int mem_cgroup_do_precharge(unsigned long count)
> return ret;
> }
>
> - /* Try charges one by one with reclaim */
> + /*
> + * Try charges one by one with reclaim, but do not retry. This avoids
> + * calling the oom killer when the precharge should just fail.
> + */
> while (count--) {
> - ret = try_charge(mc.to, GFP_KERNEL & ~__GFP_NORETRY, 1);
> + ret = try_charge(mc.to, GFP_KERNEL | __GFP_NORETRY, 1);
> if (ret)
> return ret;
> mc.precharge++;
--
Michal Hocko
SUSE Labs
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