Re: [PATCH 04/14] net: tcp_memcontrol: remove bogus hierarchy pressure propagation

Vladimir Davydov
2015-11-20T09:08:00Z

On Thu, Nov 12, 2015 at 06:41:23PM -0500, Johannes Weiner wrote:
> When a cgroup currently breaches its socket memory limit, it enters
> memory pressure mode for itself and its *ancestors*. This throttles
> transmission in unrelated sibling and cousin subtrees that have
> nothing to do with the breached limit.
>
> On the contrary, breaching a limit should make that group and its
> *children* enter memory pressure mode. But this happens already,
> albeit lazily: if an ancestor limit is breached, siblings will enter
> memory pressure on their own once the next packet arrives for them.

Hmm, we still call sk_prot->enter_memory_pressure, which might hurt a
workload in the root cgroup AFAICS. Strange. You fix it in patch 8
though.

>
> So no additional hierarchy code is needed. Remove the bogus stuff.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>