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

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

[Abel Wu]

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 <wuyun.abel@bytedance.com>
---
 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

[PATCH net-next 2/2] net-memcg: Remove redundant tcpmem_pressure

[Abel Wu]

As {socket,tcpmem}_pressure are only used in default/legacy mode
respectively, use socket_pressure instead of tcpmem_pressure in all
kinds of cgroup hierarchies.

Signed-off-by: Abel Wu <wuyun.abel@bytedance.com>
---
 include/linux/memcontrol.h | 3 +--
 mm/memcontrol.c            | 4 ++--
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 9b1b536b4ec9..05e9fb5fa08d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -288,7 +288,6 @@ struct mem_cgroup {
 
 	/* Legacy tcp memory accounting */
 	bool			tcpmem_active;
-	int			tcpmem_pressure;
 
 #ifdef CONFIG_MEMCG_KMEM
 	int kmemcg_id;
@@ -1744,7 +1743,7 @@ 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))
-		return !!memcg->tcpmem_pressure;
+		return !!memcg->socket_pressure;
 	do {
 		if (time_before(jiffies, READ_ONCE(memcg->socket_pressure)))
 			return true;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4b27e245a055..76c4e5c6e558 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7337,10 +7337,10 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
 		struct page_counter *fail;
 
 		if (page_counter_try_charge(&memcg->tcpmem, nr_pages, &fail)) {
-			memcg->tcpmem_pressure = 0;
+			memcg->socket_pressure = 0;
 			return true;
 		}
-		memcg->tcpmem_pressure = 1;
+		memcg->socket_pressure = 1;
 		if (gfp_mask & __GFP_NOFAIL) {
 			page_counter_charge(&memcg->tcpmem, nr_pages);
 			return true;
-- 
2.37.3

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

[Jakub Kicinski]

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