From 345aa031207d02d7438c1aa96ed9315911ecd745 Mon Sep 17 00:00:00 2001 From: Jarek Poplawski Date: Tue, 7 Jul 2009 19:39:16 -0700 Subject: ipv4: Fix fib_trie rebalancing, part 4 (root thresholds) Pawel Staszewski wrote:
Some time ago i report this: http://bugzilla.kernel.org/show_bug.cgi?id=6648 and now with 2.6.29 / 2.6.29.1 / 2.6.29.3 and 2.6.30 it back dmesg output: oprofile: using NMI interrupt. Fix inflate_threshold_root. Now=15 size=11 bits ... Fix inflate_threshold_root. Now=15 size=11 bits cat /proc/net/fib_triestat Basic info: size of leaf: 40 bytes, size of tnode: 56 bytes. Main: Aver depth: 2.28 Max depth: 6 Leaves: 276539 Prefixes: 289922 Internal nodes: 66762 1: 35046 2: 13824 3: 9508 4: 4897 5: 2331 6: 1149 7: 5 9: 1 18: 1 Pointers: 691228 Null ptrs: 347928 Total size: 35709 kB
It seems, the current threshold for root resizing is too aggressive, and it causes misleading warnings during big updates, but it might be also responsible for memory problems, especially with non-preempt configs, when RCU freeing is delayed long after call_rcu. It should be also mentioned that because of non-atomic changes during resizing/rebalancing the current lookup algorithm can miss valid leaves so it's additional argument to shorten these activities even at a cost of a minimally longer searching. This patch restores values before the patch "[IPV4]: fib_trie root node settings", commit: 965ffea43d4ebe8cd7b9fee78d651268dd7d23c5 from v2.6.22. Pawel's report:
I dont see any big change of (cpu load or faster/slower routing/propagating routes from bgpd or something else) - in avg there is from 2% to 3% more of CPU load i dont know why but it is - i change from "preempt" to "no preempt" 3 times and check this my "mpstat -P ALL 1 30" always avg cpu load was from 2 to 3% more compared to "no preempt" [...] cat /proc/net/fib_triestat Basic info: size of leaf: 20 bytes, size of tnode: 36 bytes. Main: Aver depth: 2.44 Max depth: 6 Leaves: 277814 Prefixes: 291306 Internal nodes: 66420 1: 32737 2: 14850 3: 10332 4: 4871 5: 2313 6: 942 7: 371 8: 3 17: 1 Pointers: 599098 Null ptrs: 254865 Total size: 18067 kB
According to this and other similar reports average depth is slightly increased (~0.2), and root nodes are shorter (log 17 vs. 18), but there is no visible performance decrease. So, until memory handling is improved or added parameters for changing this individually, this patch resets to safer defaults. Reported-by: Pawel Staszewski Reported-by: Jorge Boncompte [DTI2] Signed-off-by: Jarek Poplawski Tested-by: Pawel Staszewski Signed-off-by: David S. Miller --- net/ipv4/fib_trie.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 00a54b246dfe..63c2fa7b68c4 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -316,8 +316,8 @@ static inline void check_tnode(const struct tnode *tn) static const int halve_threshold = 25; static const int inflate_threshold = 50; -static const int halve_threshold_root = 8; -static const int inflate_threshold_root = 15; +static const int halve_threshold_root = 15; +static const int inflate_threshold_root = 25; static void __alias_free_mem(struct rcu_head *head) -- cgit v1.2.3 From a57de0b4336e48db2811a2030bb68dba8dd09d88 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 8 Jul 2009 12:09:13 +0000 Subject: net: adding memory barrier to the poll and receive callbacks Adding memory barrier after the poll_wait function, paired with receive callbacks. Adding fuctions sock_poll_wait and sk_has_sleeper to wrap the memory barrier. Without the memory barrier, following race can happen. The race fires, when following code paths meet, and the tp->rcv_nxt and __add_wait_queue updates stay in CPU caches. CPU1 CPU2 sys_select receive packet ... ... __add_wait_queue update tp->rcv_nxt ... ... tp->rcv_nxt check sock_def_readable ... { schedule ... if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) wake_up_interruptible(sk->sk_sleep) ... } If there was no cache the code would work ok, since the wait_queue and rcv_nxt are opposit to each other. Meaning that once tp->rcv_nxt is updated by CPU2, the CPU1 either already passed the tp->rcv_nxt check and sleeps, or will get the new value for tp->rcv_nxt and will return with new data mask. In both cases the process (CPU1) is being added to the wait queue, so the waitqueue_active (CPU2) call cannot miss and will wake up CPU1. The bad case is when the __add_wait_queue changes done by CPU1 stay in its cache, and so does the tp->rcv_nxt update on CPU2 side. The CPU1 will then endup calling schedule and sleep forever if there are no more data on the socket. Calls to poll_wait in following modules were ommited: net/bluetooth/af_bluetooth.c net/irda/af_irda.c net/irda/irnet/irnet_ppp.c net/mac80211/rc80211_pid_debugfs.c net/phonet/socket.c net/rds/af_rds.c net/rfkill/core.c net/sunrpc/cache.c net/sunrpc/rpc_pipe.c net/tipc/socket.c Signed-off-by: Jiri Olsa Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/sock.h | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++ net/atm/common.c | 6 ++--- net/core/datagram.c | 2 +- net/core/sock.c | 8 +++---- net/dccp/output.c | 2 +- net/dccp/proto.c | 2 +- net/ipv4/tcp.c | 2 +- net/iucv/af_iucv.c | 4 ++-- net/rxrpc/af_rxrpc.c | 4 ++-- net/unix/af_unix.c | 8 +++---- 10 files changed, 85 insertions(+), 19 deletions(-) (limited to 'net/ipv4') diff --git a/include/net/sock.h b/include/net/sock.h index 352f06bbd7a9..4eb8409249f6 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -54,6 +54,7 @@ #include #include +#include #include #include @@ -1241,6 +1242,71 @@ static inline int sk_has_allocations(const struct sock *sk) return sk_wmem_alloc_get(sk) || sk_rmem_alloc_get(sk); } +/** + * sk_has_sleeper - check if there are any waiting processes + * @sk: socket + * + * Returns true if socket has waiting processes + * + * The purpose of the sk_has_sleeper and sock_poll_wait is to wrap the memory + * barrier call. They were added due to the race found within the tcp code. + * + * Consider following tcp code paths: + * + * CPU1 CPU2 + * + * sys_select receive packet + * ... ... + * __add_wait_queue update tp->rcv_nxt + * ... ... + * tp->rcv_nxt check sock_def_readable + * ... { + * schedule ... + * if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + * wake_up_interruptible(sk->sk_sleep) + * ... + * } + * + * The race for tcp fires when the __add_wait_queue changes done by CPU1 stay + * in its cache, and so does the tp->rcv_nxt update on CPU2 side. The CPU1 + * could then endup calling schedule and sleep forever if there are no more + * data on the socket. + */ +static inline int sk_has_sleeper(struct sock *sk) +{ + /* + * We need to be sure we are in sync with the + * add_wait_queue modifications to the wait queue. + * + * This memory barrier is paired in the sock_poll_wait. + */ + smp_mb(); + return sk->sk_sleep && waitqueue_active(sk->sk_sleep); +} + +/** + * sock_poll_wait - place memory barrier behind the poll_wait call. + * @filp: file + * @wait_address: socket wait queue + * @p: poll_table + * + * See the comments in the sk_has_sleeper function. + */ +static inline void sock_poll_wait(struct file *filp, + wait_queue_head_t *wait_address, poll_table *p) +{ + if (p && wait_address) { + poll_wait(filp, wait_address, p); + /* + * We need to be sure we are in sync with the + * socket flags modification. + * + * This memory barrier is paired in the sk_has_sleeper. + */ + smp_mb(); + } +} + /* * Queue a received datagram if it will fit. Stream and sequenced * protocols can't normally use this as they need to fit buffers in diff --git a/net/atm/common.c b/net/atm/common.c index c1c97936192c..8c4d843eb17f 100644 --- a/net/atm/common.c +++ b/net/atm/common.c @@ -92,7 +92,7 @@ static void vcc_sock_destruct(struct sock *sk) static void vcc_def_wakeup(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up(sk->sk_sleep); read_unlock(&sk->sk_callback_lock); } @@ -110,7 +110,7 @@ static void vcc_write_space(struct sock *sk) read_lock(&sk->sk_callback_lock); if (vcc_writable(sk)) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); @@ -594,7 +594,7 @@ unsigned int vcc_poll(struct file *file, struct socket *sock, poll_table *wait) struct atm_vcc *vcc; unsigned int mask; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); mask = 0; vcc = ATM_SD(sock); diff --git a/net/core/datagram.c b/net/core/datagram.c index 58abee1f1df1..b0fe69211eef 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -712,7 +712,7 @@ unsigned int datagram_poll(struct file *file, struct socket *sock, struct sock *sk = sock->sk; unsigned int mask; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); mask = 0; /* exceptional events? */ diff --git a/net/core/sock.c b/net/core/sock.c index b0ba569bc973..6354863b1c68 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1715,7 +1715,7 @@ EXPORT_SYMBOL(sock_no_sendpage); static void sock_def_wakeup(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_all(sk->sk_sleep); read_unlock(&sk->sk_callback_lock); } @@ -1723,7 +1723,7 @@ static void sock_def_wakeup(struct sock *sk) static void sock_def_error_report(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_poll(sk->sk_sleep, POLLERR); sk_wake_async(sk, SOCK_WAKE_IO, POLL_ERR); read_unlock(&sk->sk_callback_lock); @@ -1732,7 +1732,7 @@ static void sock_def_error_report(struct sock *sk) static void sock_def_readable(struct sock *sk, int len) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_sync_poll(sk->sk_sleep, POLLIN | POLLRDNORM | POLLRDBAND); sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); @@ -1747,7 +1747,7 @@ static void sock_def_write_space(struct sock *sk) * progress. --DaveM */ if ((atomic_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_sync_poll(sk->sk_sleep, POLLOUT | POLLWRNORM | POLLWRBAND); diff --git a/net/dccp/output.c b/net/dccp/output.c index c0e88c16d088..c96119fda688 100644 --- a/net/dccp/output.c +++ b/net/dccp/output.c @@ -196,7 +196,7 @@ void dccp_write_space(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible(sk->sk_sleep); /* Should agree with poll, otherwise some programs break */ if (sock_writeable(sk)) diff --git a/net/dccp/proto.c b/net/dccp/proto.c index 314a1b5c033c..94ca8eaace7d 100644 --- a/net/dccp/proto.c +++ b/net/dccp/proto.c @@ -311,7 +311,7 @@ unsigned int dccp_poll(struct file *file, struct socket *sock, unsigned int mask; struct sock *sk = sock->sk; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); if (sk->sk_state == DCCP_LISTEN) return inet_csk_listen_poll(sk); diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 7870a535dac6..91145244ea63 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -339,7 +339,7 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait) struct sock *sk = sock->sk; struct tcp_sock *tp = tcp_sk(sk); - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); if (sk->sk_state == TCP_LISTEN) return inet_csk_listen_poll(sk); diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c index 6be5f92d1094..49c15b48408e 100644 --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -306,7 +306,7 @@ static inline int iucv_below_msglim(struct sock *sk) static void iucv_sock_wake_msglim(struct sock *sk) { read_lock(&sk->sk_callback_lock); - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_all(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); read_unlock(&sk->sk_callback_lock); @@ -1256,7 +1256,7 @@ unsigned int iucv_sock_poll(struct file *file, struct socket *sock, struct sock *sk = sock->sk; unsigned int mask = 0; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); if (sk->sk_state == IUCV_LISTEN) return iucv_accept_poll(sk); diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c index eac5e7bb7365..bfe493ebf27c 100644 --- a/net/rxrpc/af_rxrpc.c +++ b/net/rxrpc/af_rxrpc.c @@ -63,7 +63,7 @@ static void rxrpc_write_space(struct sock *sk) _enter("%p", sk); read_lock(&sk->sk_callback_lock); if (rxrpc_writable(sk)) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); } @@ -588,7 +588,7 @@ static unsigned int rxrpc_poll(struct file *file, struct socket *sock, unsigned int mask; struct sock *sk = sock->sk; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); mask = 0; /* the socket is readable if there are any messages waiting on the Rx diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 36d4e44d6233..fc3ebb906911 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -315,7 +315,7 @@ static void unix_write_space(struct sock *sk) { read_lock(&sk->sk_callback_lock); if (unix_writable(sk)) { - if (sk->sk_sleep && waitqueue_active(sk->sk_sleep)) + if (sk_has_sleeper(sk)) wake_up_interruptible_sync(sk->sk_sleep); sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); } @@ -1985,7 +1985,7 @@ static unsigned int unix_poll(struct file *file, struct socket *sock, poll_table struct sock *sk = sock->sk; unsigned int mask; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); mask = 0; /* exceptional events? */ @@ -2022,7 +2022,7 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, struct sock *sk = sock->sk, *other; unsigned int mask, writable; - poll_wait(file, sk->sk_sleep, wait); + sock_poll_wait(file, sk->sk_sleep, wait); mask = 0; /* exceptional events? */ @@ -2053,7 +2053,7 @@ static unsigned int unix_dgram_poll(struct file *file, struct socket *sock, other = unix_peer_get(sk); if (other) { if (unix_peer(other) != sk) { - poll_wait(file, &unix_sk(other)->peer_wait, + sock_poll_wait(file, &unix_sk(other)->peer_wait, wait); if (unix_recvq_full(other)) writable = 0; -- cgit v1.2.3