[PATCH] mm: proc: add Sock to /proc/meminfo

Muchun Song
2020-10-10T22:58:57Z

The amount of memory allocated to sockets buffer can become significant.
However, we do not display the amount of memory consumed by sockets
buffer. In this case, knowing where the memory is consumed by the kernel
is very difficult. On our server with 500GB RAM, sometimes we can see
25GB disappear through /proc/meminfo. After our analysis, we found the
following memory allocation path which consumes the memory with page_owner
enabled.

849698 times:
Page allocated via order 3, mask 0x4052c0(GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP)
__alloc_pages_nodemask+0x11d/0x290
skb_page_frag_refill+0x68/0xf0
sk_page_frag_refill+0x19/0x70
tcp_sendmsg_locked+0x2f4/0xd10
tcp_sendmsg+0x29/0xa0
sock_sendmsg+0x30/0x40
sock_write_iter+0x8f/0x100
__vfs_write+0x10b/0x190
vfs_write+0xb0/0x190
ksys_write+0x5a/0xd0
do_syscall_64+0x5d/0x110
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
drivers/base/node.c | 2 ++
drivers/net/virtio_net.c | 3 +--
fs/proc/meminfo.c | 1 +
include/linux/mmzone.h | 1 +
include/linux/skbuff.h | 43 ++++++++++++++++++++++++++++++++++++++--
kernel/exit.c | 3 +--
mm/page_alloc.c | 7 +++++--
mm/vmstat.c | 1 +
net/core/sock.c | 8 ++++----
net/ipv4/tcp.c | 3 +--
net/xfrm/xfrm_state.c | 3 +--
11 files changed, 59 insertions(+), 16 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 508b80f6329b..6f92775da85c 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -418,6 +418,7 @@ static ssize_t node_read_meminfo(struct device *dev,
#ifdef CONFIG_SHADOW_CALL_STACK
"Node %d ShadowCallStack:%8lu kB\n"
#endif
+ "Node %d Sock: %8lu kB\n"
"Node %d PageTables: %8lu kB\n"
"Node %d NFS_Unstable: %8lu kB\n"
"Node %d Bounce: %8lu kB\n"
@@ -441,6 +442,7 @@ static ssize_t node_read_meminfo(struct device *dev,
nid, K(node_page_state(pgdat, NR_ANON_MAPPED)),
nid, K(i.sharedram),
nid, node_page_state(pgdat, NR_KERNEL_STACK_KB),
+ nid, K(node_page_state(pgdat, NR_SOCK)),
#ifdef CONFIG_SHADOW_CALL_STACK
nid, node_page_state(pgdat, NR_KERNEL_SCS_KB),
#endif
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 263b005981bd..e7183f67ae4a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2646,8 +2646,7 @@ static void free_receive_page_frags(struct virtnet_info *vi)
{
int i;
for (i = 0; i < vi->max_queue_pairs; i++)
- if (vi->rq[i].alloc_frag.page)
- put_page(vi->rq[i].alloc_frag.page);
+ put_page_frag(&vi->rq[i].alloc_frag);
}

static void free_unused_bufs(struct virtnet_info *vi)
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 887a5532e449..1dcf3120d831 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -106,6 +106,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
seq_printf(m, "ShadowCallStack:%8lu kB\n",
global_node_page_state(NR_KERNEL_SCS_KB));
#endif
+ show_val_kb(m, "Sock: ", global_node_page_state(NR_SOCK));
show_val_kb(m, "PageTables: ",
global_zone_page_state(NR_PAGETABLE));

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 31712bb61f7f..1996713d2c6b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -207,6 +207,7 @@ enum node_stat_item {
#if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
NR_KERNEL_SCS_KB, /* measured in KiB */
#endif
+ NR_SOCK, /* Count of socket buffer pages */
NR_VM_NODE_STAT_ITEMS
};

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index fcd53f97c186..7e5108da4d84 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -19,7 +19,8 @@
#include <linux/rbtree.h>
#include <linux/socket.h>
#include <linux/refcount.h>
-
+#include <linux/memcontrol.h>
+#include <linux/mm.h>
#include <linux/atomic.h>
#include <asm/types.h>
#include <linux/spinlock.h>
@@ -3003,6 +3004,25 @@ static inline void skb_frag_ref(struct sk_buff *skb, int f)
__skb_frag_ref(&skb_shinfo(skb)->frags[f]);
}

+static inline void inc_sock_node_page_state(struct page *page)
+{
+ mod_node_page_state(page_pgdat(page), NR_SOCK, compound_nr(page));
+ /*
+ * Indicate that we need to decrease the Sock page state when
+ * the page freed.
+ */
+ SetPagePrivate(page);
+}
+
+static inline void dec_sock_node_page_state(struct page *page)
+{
+ if (PagePrivate(page)) {
+ ClearPagePrivate(page);
+ mod_node_page_state(page_pgdat(page), NR_SOCK,
+ -compound_nr(page));
+ }
+}
+
/**
* __skb_frag_unref - release a reference on a paged fragment.
* @frag: the paged fragment
@@ -3011,7 +3031,12 @@ static inline void skb_frag_ref(struct sk_buff *skb, int f)
*/
static inline void __skb_frag_unref(skb_frag_t *frag)
{
- put_page(skb_frag_page(frag));
+ struct page *page = skb_frag_page(frag);
+
+ if (put_page_testzero(page)) {
+ dec_sock_node_page_state(page);
+ __put_page(page);
+ }
}

/**
@@ -3091,6 +3116,20 @@ static inline void skb_frag_set_page(struct sk_buff *skb, int f,
__skb_frag_set_page(&skb_shinfo(skb)->frags[f], page);
}

+static inline bool put_page_frag(struct page_frag *pfrag)
+{
+ struct page *page = pfrag->page;
+
+ if (page) {
+ if (put_page_testzero(page)) {
+ dec_sock_node_page_state(page);
+ __put_page(page);
+ }
+ return true;
+ }
+ return false;
+}
+
bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t prio);

/**
diff --git a/kernel/exit.c b/kernel/exit.c
index 62912406d74a..58d373767d16 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -841,8 +841,7 @@ void __noreturn do_exit(long code)
if (tsk->splice_pipe)
free_pipe_info(tsk->splice_pipe);

- if (tsk->task_frag.page)
- put_page(tsk->task_frag.page);
+ put_page_frag(&tsk->task_frag);

validate_creds_for_do_exit(tsk);

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cefbef32bf4a..6c543158aa06 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5379,7 +5379,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
" unevictable:%lu dirty:%lu writeback:%lu\n"
" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
- " free:%lu free_pcp:%lu free_cma:%lu\n",
+ " free:%lu free_pcp:%lu free_cma:%lu sock:%lu\n",
global_node_page_state(NR_ACTIVE_ANON),
global_node_page_state(NR_INACTIVE_ANON),
global_node_page_state(NR_ISOLATED_ANON),
@@ -5397,7 +5397,8 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
global_zone_page_state(NR_BOUNCE),
global_zone_page_state(NR_FREE_PAGES),
free_pcp,
- global_zone_page_state(NR_FREE_CMA_PAGES));
+ global_zone_page_state(NR_FREE_CMA_PAGES),
+ global_node_page_state(NR_SOCK));

for_each_online_pgdat(pgdat) {
if (show_mem_node_skip(filter, pgdat->node_id, nodemask))
@@ -5425,6 +5426,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
#ifdef CONFIG_SHADOW_CALL_STACK
" shadow_call_stack:%lukB"
#endif
+ " sock:%lukB"
" all_unreclaimable? %s"
"\n",
pgdat->node_id,
@@ -5450,6 +5452,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
#ifdef CONFIG_SHADOW_CALL_STACK
node_page_state(pgdat, NR_KERNEL_SCS_KB),
#endif
+ K(node_page_state(pgdat, NR_SOCK)),
pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
"yes" : "no");
}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index b05dec387557..ceaf6f85c155 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1220,6 +1220,7 @@ const char * const vmstat_text[] = {
#if IS_ENABLED(CONFIG_SHADOW_CALL_STACK)
"nr_shadow_call_stack",
#endif
+ "nr_sock",

/* enum writeback_stat_item counters */
"nr_dirty_threshold",
diff --git a/net/core/sock.c b/net/core/sock.c
index 5972d26f03ae..1661b423802b 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1780,10 +1780,8 @@ static void __sk_destruct(struct rcu_head *head)
pr_debug("%s: optmem leakage (%d bytes) detected\n",
__func__, atomic_read(&sk->sk_omem_alloc));

- if (sk->sk_frag.page) {
- put_page(sk->sk_frag.page);
+ if (put_page_frag(&sk->sk_frag))
sk->sk_frag.page = NULL;
- }

if (sk->sk_peer_cred)
put_cred(sk->sk_peer_cred);
@@ -2456,7 +2454,7 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp)
}
if (pfrag->offset + sz <= pfrag->size)
return true;
- put_page(pfrag->page);
+ put_page_frag(pfrag);
}

pfrag->offset = 0;
@@ -2469,12 +2467,14 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp)
SKB_FRAG_PAGE_ORDER);
if (likely(pfrag->page)) {
pfrag->size = PAGE_SIZE << SKB_FRAG_PAGE_ORDER;
+ inc_sock_node_page_state(pfrag->page);
return true;
}
}
pfrag->page = alloc_page(gfp);
if (likely(pfrag->page)) {
pfrag->size = PAGE_SIZE;
+ inc_sock_node_page_state(pfrag->page);
return true;
}
return false;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 57a568875539..583761844b4f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2751,8 +2751,7 @@ int tcp_disconnect(struct sock *sk, int flags)

WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);

- if (sk->sk_frag.page) {
- put_page(sk->sk_frag.page);
+ if (put_page_frag(&sk->sk_frag)) {
sk->sk_frag.page = NULL;
sk->sk_frag.offset = 0;
}
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 69520ad3d83b..0f7c16679e49 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -495,8 +495,7 @@ static void ___xfrm_state_destroy(struct xfrm_state *x)
x->type->destructor(x);
xfrm_put_type(x->type);
}
- if (x->xfrag.page)
- put_page(x->xfrag.page);
+ put_page_frag(&x->xfrag);
xfrm_dev_state_free(x);
security_xfrm_state_free(x);
xfrm_state_free(x);
--
2.20.1