[PATCH net-next 0/3] net: better packing of global vars

[PATCH net-next 0/3] net: better packing of global vars

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

First two patches avoid holes in data section,
and last patch makes sure some siphash keys are contained
in a single cache line.

Eric Dumazet (3):
  once: use __section(".data.once")
  net: use .data.once section in netdev_level_once()
  net: align static siphash keys

 include/linux/netdevice.h            | 2 +-
 include/linux/once.h                 | 2 +-
 include/linux/siphash.h              | 2 ++
 net/core/flow_dissector.c            | 2 +-
 net/core/secure_seq.c                | 4 ++--
 net/ipv4/route.c                     | 2 +-
 net/ipv4/syncookies.c                | 2 +-
 net/ipv6/route.c                     | 2 +-
 net/ipv6/syncookies.c                | 2 +-
 net/netfilter/nf_conntrack_core.c    | 4 ++--
 net/netfilter/nf_conntrack_expect.c  | 2 +-
 net/netfilter/nf_conntrack_netlink.c | 2 +-
 net/netfilter/nf_nat_core.c          | 2 +-
 13 files changed, 16 insertions(+), 14 deletions(-)

-- 
2.34.0.rc1.387.gb447b232ab-goog

[PATCH net-next 1/3] once: use __section(".data.once")

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

.data.once contains nicely packed bool variables.
It is used already by DO_ONCE_LITE().

Using it also in DO_ONCE() removes holes in .data section.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/once.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/once.h b/include/linux/once.h
index d361fb14ac3a2c5b77c289107f093862194ebd1c..f54523052bbcb5d0c13017d4684b68ceb8da5855 100644
--- a/include/linux/once.h
+++ b/include/linux/once.h
@@ -38,7 +38,7 @@ void __do_once_done(bool *done, struct static_key_true *once_key,
 #define DO_ONCE(func, ...)						     \
 	({								     \
 		bool ___ret = false;					     \
-		static bool ___done = false;				     \
+		static bool __section(".data.once") ___done = false;	     \
 		static DEFINE_STATIC_KEY_TRUE(___once_key);		     \
 		if (static_branch_unlikely(&___once_key)) {		     \
 			unsigned long ___flags;				     \
-- 
2.34.0.rc1.387.gb447b232ab-goog

[PATCH net-next 2/3] net: use .data.once section in netdev_level_once()

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Same rationale than prior patch : using the dedicated
section avoid holes and pack all these bool values.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/netdevice.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3ec42495a43a56dbd51fecd166d572a9e586e3e4..e6beb603537572aae64e33ea2c739741b4f97ce5 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -5291,7 +5291,7 @@ void netdev_info(const struct net_device *dev, const char *format, ...);
 
 #define netdev_level_once(level, dev, fmt, ...)			\
 do {								\
-	static bool __print_once __read_mostly;			\
+	static bool __section(".data.once") __print_once;	\
 								\
 	if (!__print_once) {					\
 		__print_once = true;				\
-- 
2.34.0.rc1.387.gb447b232ab-goog

[PATCH net-next 3/3] net: align static siphash keys

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

siphash keys use 16 bytes.

Define siphash_aligned_key_t macro so that we can make sure they
are not crossing a cache line boundary.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/siphash.h              | 2 ++
 net/core/flow_dissector.c            | 2 +-
 net/core/secure_seq.c                | 4 ++--
 net/ipv4/route.c                     | 2 +-
 net/ipv4/syncookies.c                | 2 +-
 net/ipv6/route.c                     | 2 +-
 net/ipv6/syncookies.c                | 2 +-
 net/netfilter/nf_conntrack_core.c    | 4 ++--
 net/netfilter/nf_conntrack_expect.c  | 2 +-
 net/netfilter/nf_conntrack_netlink.c | 2 +-
 net/netfilter/nf_nat_core.c          | 2 +-
 11 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/include/linux/siphash.h b/include/linux/siphash.h
index bf21591a9e5e653585c26cb3f3f0857256c0eb89..3f7427b9e9357d98b1e21a981cf227195bbdd2aa 100644
--- a/include/linux/siphash.h
+++ b/include/linux/siphash.h
@@ -21,6 +21,8 @@ typedef struct {
 	u64 key[2];
 } siphash_key_t;
 
+#define siphash_aligned_key_t siphash_key_t __aligned(16)
+
 static inline bool siphash_key_is_zero(const siphash_key_t *key)
 {
 	return !(key->key[0] | key->key[1]);
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 3255f57f5131af315f0148909e69ff4c91e66b94..257976cb55cee86ae16623e240c553eb78ad433f 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1460,7 +1460,7 @@ bool __skb_flow_dissect(const struct net *net,
 }
 EXPORT_SYMBOL(__skb_flow_dissect);
 
-static siphash_key_t hashrnd __read_mostly;
+static siphash_aligned_key_t hashrnd;
 static __always_inline void __flow_hash_secret_init(void)
 {
 	net_get_random_once(&hashrnd, sizeof(hashrnd));
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index b5bc680d475536de6da68a9a8815691cf81176a6..9b8443774449f5bb8cd2c62ca34eedf139eeb3ed 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -19,8 +19,8 @@
 #include <linux/in6.h>
 #include <net/tcp.h>
 
-static siphash_key_t net_secret __read_mostly;
-static siphash_key_t ts_secret __read_mostly;
+static siphash_aligned_key_t net_secret;
+static siphash_aligned_key_t ts_secret;
 
 static __always_inline void net_secret_init(void)
 {
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 0b4103b1e6220f97f11a75f960476c161ccb3f39..243a0c52be42b60226a38dce980956b33e583d80 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -602,7 +602,7 @@ static void fnhe_remove_oldest(struct fnhe_hash_bucket *hash)
 
 static u32 fnhe_hashfun(__be32 daddr)
 {
-	static siphash_key_t fnhe_hash_key __read_mostly;
+	static siphash_aligned_key_t fnhe_hash_key;
 	u64 hval;
 
 	net_get_random_once(&fnhe_hash_key, sizeof(fnhe_hash_key));
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 8696dc343ad2cd08fabfb714a32ac67459e4df7e..2cb3b852d14861231ac47f0b3e4daeb57682ffd2 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -14,7 +14,7 @@
 #include <net/tcp.h>
 #include <net/route.h>
 
-static siphash_key_t syncookie_secret[2] __read_mostly;
+static siphash_aligned_key_t syncookie_secret[2];
 
 #define COOKIEBITS 24	/* Upper bits store count */
 #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3ae25b8ffbd6fbeda4b46438dc14b11235558f10..5e8f2f15607db7e6589b8bdb984e62512ad30589 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1485,7 +1485,7 @@ static void rt6_exception_remove_oldest(struct rt6_exception_bucket *bucket)
 static u32 rt6_exception_hash(const struct in6_addr *dst,
 			      const struct in6_addr *src)
 {
-	static siphash_key_t rt6_exception_key __read_mostly;
+	static siphash_aligned_key_t rt6_exception_key;
 	struct {
 		struct in6_addr dst;
 		struct in6_addr src;
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index e8cfb9e997bf062d24cf3e4d4e95a447890c7952..d1b61d00368e1f58725e9997f74a0b144901277e 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -20,7 +20,7 @@
 #define COOKIEBITS 24	/* Upper bits store count */
 #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
 
-static siphash_key_t syncookie6_secret[2] __read_mostly;
+static siphash_aligned_key_t syncookie6_secret[2];
 
 /* RFC 2460, Section 8.3:
  * [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 770a63103c7a4240b8559a97f707588d569beba8..054ee9d25efe174684025d60ea7b72e79c7ca19e 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -189,7 +189,7 @@ EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);
 unsigned int nf_conntrack_max __read_mostly;
 EXPORT_SYMBOL_GPL(nf_conntrack_max);
 seqcount_spinlock_t nf_conntrack_generation __read_mostly;
-static siphash_key_t nf_conntrack_hash_rnd __read_mostly;
+static siphash_aligned_key_t nf_conntrack_hash_rnd;
 
 static u32 hash_conntrack_raw(const struct nf_conntrack_tuple *tuple,
 			      unsigned int zoneid,
@@ -482,7 +482,7 @@ EXPORT_SYMBOL_GPL(nf_ct_invert_tuple);
  */
 u32 nf_ct_get_id(const struct nf_conn *ct)
 {
-	static __read_mostly siphash_key_t ct_id_seed;
+	static siphash_aligned_key_t ct_id_seed;
 	unsigned long a, b, c, d;
 
 	net_get_random_once(&ct_id_seed, sizeof(ct_id_seed));
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index f562eeef42349e6e40f15b056405dd53d9916f1e..1e89b595ecd086eb55f6fb8d9aa31f3abe2afc33 100644
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -41,7 +41,7 @@ EXPORT_SYMBOL_GPL(nf_ct_expect_hash);
 unsigned int nf_ct_expect_max __read_mostly;
 
 static struct kmem_cache *nf_ct_expect_cachep __read_mostly;
-static siphash_key_t nf_ct_expect_hashrnd __read_mostly;
+static siphash_aligned_key_t nf_ct_expect_hashrnd;
 
 /* nf_conntrack_expect helper functions */
 void nf_ct_unlink_expect_report(struct nf_conntrack_expect *exp,
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index f1e5443fe7c74cde3f5f0a1a01bcbe530bedb75c..3d6c8da3de1fbbfc64dea06ab5946f9e79ff72ee 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -2997,7 +2997,7 @@ static const union nf_inet_addr any_addr;
 
 static __be32 nf_expect_get_id(const struct nf_conntrack_expect *exp)
 {
-	static __read_mostly siphash_key_t exp_id_seed;
+	static siphash_aligned_key_t exp_id_seed;
 	unsigned long a, b, c, d;
 
 	net_get_random_once(&exp_id_seed, sizeof(exp_id_seed));
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 4d50d51db796276c84fbc3486b870bd591d93796..ab9f6c75524d80c9d3ef032c9911e60b02206b88 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -34,7 +34,7 @@ static unsigned int nat_net_id __read_mostly;
 
 static struct hlist_head *nf_nat_bysource __read_mostly;
 static unsigned int nf_nat_htable_size __read_mostly;
-static siphash_key_t nf_nat_hash_rnd __read_mostly;
+static siphash_aligned_key_t nf_nat_hash_rnd;
 
 struct nf_nat_lookup_hook_priv {
 	struct nf_hook_entries __rcu *entries;
-- 
2.34.0.rc1.387.gb447b232ab-goog

Re: [PATCH net-next 0/3] net: better packing of global vars

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 15 Nov 2021 09:23:00 -0800 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> First two patches avoid holes in data section,
> and last patch makes sure some siphash keys are contained
> in a single cache line.
> 
> Eric Dumazet (3):
>   once: use __section(".data.once")
>   net: use .data.once section in netdev_level_once()
>   net: align static siphash keys
> 
> [...]

Here is the summary with links:
  - [net-next,1/3] once: use __section(".data.once")
    https://git.kernel.org/netdev/net-next/c/c2c60ea37e5b
  - [net-next,2/3] net: use .data.once section in netdev_level_once()
    https://git.kernel.org/netdev/net-next/c/7071732c26fe
  - [net-next,3/3] net: align static siphash keys
    https://git.kernel.org/netdev/net-next/c/49ecc2e9c3ab

You are awesome, thank you!
-- 
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