[PATCH net-next 2/2] net: avoid calling sched_clock when LLS is off
From: Eliezer Tamir <hidden>
Date: 2013-06-28 12:59:41
Also in:
lkml
Subsystem:
filesystems (vfs and infrastructure), networking [general], the rest · Maintainers:
Alexander Viro, Christian Brauner, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Change Low Latency Sockets code for select and poll so that when LLS is disabled sched_clock() is never called. Also, avoid sending POLL_LL to sockets if disabled. Reported-by: Andi Kleen <redacted> Signed-off-by: Eliezer Tamir <redacted> --- fs/select.c | 11 +++++++---- include/net/ll_poll.h | 17 +++++++++++++++-- 2 files changed, 22 insertions(+), 6 deletions(-)
diff --git a/fs/select.c b/fs/select.c
index 79b876e..3654075 100644
--- a/fs/select.c
+++ b/fs/select.c@@ -402,7 +402,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time) poll_table *wait; int retval, i, timed_out = 0; unsigned long slack = 0; - unsigned int ll_flag = POLL_LL; + unsigned int ll_flag = ll_get_flag(); u64 ll_time = ll_end_time(); rcu_read_lock();
@@ -497,7 +497,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time) break; } - if (can_ll && can_poll_ll(ll_time)) + /* only if on, have sockets with POLL_LL and not out of time */ + if (ll_flag && can_ll && can_poll_ll(ll_time)) continue; /*
@@ -768,7 +769,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list, ktime_t expire, *to = NULL; int timed_out = 0, count = 0; unsigned long slack = 0; - unsigned int ll_flag = POLL_LL; + unsigned int ll_flag = ll_get_flag(); u64 ll_time = ll_end_time(); /* Optimise the no-wait case */
@@ -817,8 +818,10 @@ static int do_poll(unsigned int nfds, struct poll_list *list, if (count || timed_out) break; - if (can_ll && can_poll_ll(ll_time)) + /* only if on, have sockets with POLL_LL and not out of time */ + if (ll_flag && can_ll && can_poll_ll(ll_time)) continue; + /* * If this is the first loop and we have a timeout * given, then we convert to ktime_t and set the to
diff --git a/include/net/ll_poll.h b/include/net/ll_poll.h
index 6d45e6f..6c06f7c 100644
--- a/include/net/ll_poll.h
+++ b/include/net/ll_poll.h@@ -37,6 +37,11 @@ extern unsigned int sysctl_net_ll_poll __read_mostly; #define LL_FLUSH_FAILED -1 #define LL_FLUSH_BUSY -2 +static inline unsigned int ll_get_flag(void) +{ + return sysctl_net_ll_poll ? POLL_LL : 0; +} + /* a wrapper to make debug_smp_processor_id() happy * we can use sched_clock() because we don't care much about precision * we only care that the average is bounded
@@ -67,10 +72,14 @@ static inline u64 ll_sk_end_time(struct sock *sk) return ((u64)ACCESS_ONCE(sk->sk_ll_usec) << 10) + ll_sched_clock(); } -/* in poll/select we use the global sysctl_net_ll_poll value */ +/* in poll/select we use the global sysctl_net_ll_poll value + * only call sched_clock() if enabled + */ static inline u64 ll_end_time(void) { - return ((u64)ACCESS_ONCE(sysctl_net_ll_poll) << 10) + ll_sched_clock(); + u64 end_time = ACCESS_ONCE(sysctl_net_ll_poll); + + return end_time ? (end_time << 10) + ll_sched_clock() : 0; } static inline bool sk_valid_ll(struct sock *sk)
@@ -141,6 +150,10 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb) } #else /* CONFIG_NET_LL_RX_POLL */ +static inline unsigned long ll_get_flag(void) +{ + return 0; +} static inline u64 sk_ll_end_time(struct sock *sk) {