This is a note to let you know that I've just added the patch titled
net: make SK_MEMORY_PCPU_RESERV tunable
to the 6.8-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-make-sk_memory_pcpu_reserv-tunable.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit abdf8f5de328642052678557043a4feb2fe6a576
Author: Adam Li <adamli@xxxxxxxxxxxxxxxxxxxxxx>
Date: Mon Feb 26 02:24:52 2024 +0000
net: make SK_MEMORY_PCPU_RESERV tunable
[ Upstream commit 12a686c2e761f1f1f6e6e2117a9ab9c6de2ac8a7 ]
This patch adds /proc/sys/net/core/mem_pcpu_rsv sysctl file,
to make SK_MEMORY_PCPU_RESERV tunable.
Commit 3cd3399dd7a8 ("net: implement per-cpu reserves for
memory_allocated") introduced per-cpu forward alloc cache:
"Implement a per-cpu cache of +1/-1 MB, to reduce number
of changes to sk->sk_prot->memory_allocated, which
would otherwise be cause of false sharing."
sk_prot->memory_allocated points to global atomic variable:
atomic_long_t tcp_memory_allocated ____cacheline_aligned_in_smp;
If increasing the per-cpu cache size from 1MB to e.g. 16MB,
changes to sk->sk_prot->memory_allocated can be further reduced.
Performance may be improved on system with many cores.
Signed-off-by: Adam Li <adamli@xxxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Christoph Lameter (Ampere) <cl@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Stable-dep-of: 3584718cf2ec ("net: fix sk_memory_allocated_{add|sub} vs softirqs")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index 3960916519557..7250c0542828b 100644
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst
@@ -206,6 +206,11 @@ Will increase power usage.
Default: 0 (off)
+mem_pcpu_rsv
+------------
+
+Per-cpu reserved forward alloc cache size in page units. Default 1MB per CPU.
+
rmem_default
------------
diff --git a/include/net/sock.h b/include/net/sock.h
index 4afb4376c97e8..6855c50a70f1b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1429,6 +1429,7 @@ sk_memory_allocated(const struct sock *sk)
/* 1 MB per cpu, in page units */
#define SK_MEMORY_PCPU_RESERVE (1 << (20 - PAGE_SHIFT))
+extern int sysctl_mem_pcpu_rsv;
static inline void
sk_memory_allocated_add(struct sock *sk, int amt)
@@ -1437,7 +1438,7 @@ sk_memory_allocated_add(struct sock *sk, int amt)
preempt_disable();
local_reserve = __this_cpu_add_return(*sk->sk_prot->per_cpu_fw_alloc, amt);
- if (local_reserve >= SK_MEMORY_PCPU_RESERVE) {
+ if (local_reserve >= READ_ONCE(sysctl_mem_pcpu_rsv)) {
__this_cpu_sub(*sk->sk_prot->per_cpu_fw_alloc, local_reserve);
atomic_long_add(local_reserve, sk->sk_prot->memory_allocated);
}
@@ -1451,7 +1452,7 @@ sk_memory_allocated_sub(struct sock *sk, int amt)
preempt_disable();
local_reserve = __this_cpu_sub_return(*sk->sk_prot->per_cpu_fw_alloc, amt);
- if (local_reserve <= -SK_MEMORY_PCPU_RESERVE) {
+ if (local_reserve <= -READ_ONCE(sysctl_mem_pcpu_rsv)) {
__this_cpu_sub(*sk->sk_prot->per_cpu_fw_alloc, local_reserve);
atomic_long_add(local_reserve, sk->sk_prot->memory_allocated);
}
diff --git a/net/core/sock.c b/net/core/sock.c
index 5e78798456fd8..9cf404e8038a4 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -283,6 +283,7 @@ __u32 sysctl_rmem_max __read_mostly = SK_RMEM_MAX;
EXPORT_SYMBOL(sysctl_rmem_max);
__u32 sysctl_wmem_default __read_mostly = SK_WMEM_MAX;
__u32 sysctl_rmem_default __read_mostly = SK_RMEM_MAX;
+int sysctl_mem_pcpu_rsv __read_mostly = SK_MEMORY_PCPU_RESERVE;
int sysctl_tstamp_allow_data __read_mostly = 1;
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 0f0cb1465e089..986f15e5d6c41 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -30,6 +30,7 @@ static int int_3600 = 3600;
static int min_sndbuf = SOCK_MIN_SNDBUF;
static int min_rcvbuf = SOCK_MIN_RCVBUF;
static int max_skb_frags = MAX_SKB_FRAGS;
+static int min_mem_pcpu_rsv = SK_MEMORY_PCPU_RESERVE;
static int net_msg_warn; /* Unused, but still a sysctl */
@@ -407,6 +408,14 @@ static struct ctl_table net_core_table[] = {
.proc_handler = proc_dointvec_minmax,
.extra1 = &min_rcvbuf,
},
+ {
+ .procname = "mem_pcpu_rsv",
+ .data = &sysctl_mem_pcpu_rsv,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &min_mem_pcpu_rsv,
+ },
{
.procname = "dev_weight",
.data = &weight_p,
