This is a note to let you know that I've just added the patch titled
net-memcg: Fix scope of sockmem pressure indicators
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-memcg-fix-scope-of-sockmem-pressure-indicators.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e3cd7c7f780fbe7aba1db9ec6f38fea9f7a8ea4c
Author: Abel Wu <wuyun.abel@xxxxxxxxxxxxx>
Date: Mon Aug 14 15:09:11 2023 +0800
net-memcg: Fix scope of sockmem pressure indicators
[ Upstream commit ac8a52962164a50e693fa021d3564d7745b83a7f ]
Now there are two indicators of socket memory pressure sit inside
struct mem_cgroup, socket_pressure and tcpmem_pressure, indicating
memory reclaim pressure in memcg->memory and ->tcpmem respectively.
When in legacy mode (cgroupv1), the socket memory is charged into
->tcpmem which is independent of ->memory, so socket_pressure has
nothing to do with socket's pressure at all. Things could be worse
by taking socket_pressure into consideration in legacy mode, as a
pressure in ->memory can lead to premature reclamation/throttling
in socket.
While for the default mode (cgroupv2), the socket memory is charged
into ->memory, and ->tcpmem/->tcpmem_pressure are simply not used.
So {socket,tcpmem}_pressure are only used in default/legacy mode
respectively for indicating socket memory pressure. This patch fixes
the pieces of code that make mixed use of both.
Fixes: 8e8ae645249b ("mm: memcontrol: hook up vmpressure to socket pressure")
Signed-off-by: Abel Wu <wuyun.abel@xxxxxxxxxxxxx>
Acked-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4f189b17dafcc..94df87cb69c3b 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -310,6 +310,11 @@ struct mem_cgroup {
atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS];
atomic_long_t memory_events_local[MEMCG_NR_MEMORY_EVENTS];
+ /*
+ * Hint of reclaim pressure for socket memroy management. Note
+ * that this indicator should NOT be used in legacy cgroup mode
+ * where socket memory is accounted/charged separately.
+ */
unsigned long socket_pressure;
/* Legacy tcp memory accounting */
@@ -1627,8 +1632,8 @@ 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, memcg->socket_pressure))
return true;
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 76518e4166dc9..383e0463c0258 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);
/*
