2023-06-25 15:21:16

by Abel Wu

Subject: [PATCH net-next 1/2] net-memcg: Scopify the indicators of sockmem pressure

Now there are two indicators of socket memory pressure sit inside
struct mem_cgroup, socket_pressure and tcpmem_pressure.

When in legacy mode aka. cgroupv1, the socket memory is charged
into a separate counter memcg->tcpmem rather than ->memory, so
the reclaim pressure of the memcg has nothing to do with socket's
pressure at all. While for default mode, the ->tcpmem is simply
not used.

So {socket,tcpmem}_pressure are only used in default/legacy mode
respectively. This patch fixes the pieces of code that make mixed
use of both.

Signed-off-by: Abel Wu <[email protected]>
---
include/linux/memcontrol.h | 4 ++--
mm/vmpressure.c | 8 ++++++++
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 222d7370134c..9b1b536b4ec9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1743,8 +1743,8 @@ void mem_cgroup_sk_alloc(struct sock *sk);
void mem_cgroup_sk_free(struct sock *sk);
static inline bool mem_cgroup_under_socket_pressure(struct mem_cgroup *memcg)
{
- if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && memcg->tcpmem_pressure)
- return true;
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
+ return !!memcg->tcpmem_pressure;
do {
if (time_before(jiffies, READ_ONCE(memcg->socket_pressure)))
return true;
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index b52644771cc4..22c6689d9302 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -244,6 +244,14 @@ void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
if (mem_cgroup_disabled())
return;

+ /*
+ * The in-kernel users only care about the reclaim efficiency
+ * for this @memcg rather than the whole subtree, and there
+ * isn't and won't be any in-kernel user in a legacy cgroup.
+ */
+ if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !tree)
+ return;
+
vmpr = memcg_to_vmpressure(memcg);

/*
--
2.37.3

2023-06-26 20:08:46

by Jakub Kicinski

Subject: Re: [PATCH net-next 1/2] net-memcg: Scopify the indicators of sockmem pressure

On Sun, 25 Jun 2023 22:28:10 +0800 Abel Wu wrote:
> Now there are two indicators of socket memory pressure sit inside
> struct mem_cgroup, socket_pressure and tcpmem_pressure.
>
> When in legacy mode aka. cgroupv1, the socket memory is charged
> into a separate counter memcg->tcpmem rather than ->memory, so
> the reclaim pressure of the memcg has nothing to do with socket's
> pressure at all. While for default mode, the ->tcpmem is simply
> not used.
>
> So {socket,tcpmem}_pressure are only used in default/legacy mode
> respectively. This patch fixes the pieces of code that make mixed
> use of both.

The merge window for 6.5 has now started, let's defer this until 6.6.

Please repost in ~2 weeks.
--
pw-bot: defer