lkml.org 
[lkml]   [2013]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH net-next 2/2] net: avoid calling sched_clock when LLS is off
Date
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 <andi@firstfloor.org>
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
---

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)
{


\
 
 \ /
  Last update: 2013-06-28 15:21    [W:0.148 / U:0.516 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site