diff options
| author | Paul Turner <pjt@google.com> | 2011-11-07 20:26:33 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-11-16 08:48:18 +0100 |
| commit | 56f570e512eeb5b412cb3a62234adc446a8eb32b (patch) | |
| tree | cabaea188d6e35c077abc34fda40cc83aea9ea37 /kernel/sched.c | |
| parent | fccfdc6f0d8c83c854eeb6d93aa158f0e551bd49 (diff) | |
sched: Use jump labels to reduce overhead when bandwidth control is inactive
Now that the linkage of jump-labels has been fixed they show a measurable
improvement in overhead for the enabled-but-unused case.
Workload is:
'taskset -c 0 perf stat --repeat 50 -e instructions,cycles,branches
bash -c "for ((i=0;i<5;i++)); do $(dirname $0)/pipe-test 20000; done"'
There's a speedup for all situations:
instructions cycles branches
-------------------------------------------------------------------------
Intel Westmere
base 806611770 745895590 146765378
+jumplabel 803090165 (-0.44%) 713381840 (-4.36%) 144561130
AMD Barcelona
base 824657415 740055589 148855354
+jumplabel 821056910 (-0.44%) 737558389 (-0.34%) 146635229
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20111108042736.560831357@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 33 |
1 files changed, 31 insertions, 2 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index d6b149ccf92..d9d79a4088c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -72,6 +72,7 @@ #include <linux/ftrace.h> #include <linux/slab.h> #include <linux/init_task.h> +#include <linux/jump_label.h> #include <asm/tlb.h> #include <asm/irq_regs.h> @@ -503,7 +504,32 @@ static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) hrtimer_cancel(&cfs_b->period_timer); hrtimer_cancel(&cfs_b->slack_timer); } -#else + +#ifdef HAVE_JUMP_LABEL +static struct jump_label_key __cfs_bandwidth_used; + +static inline bool cfs_bandwidth_used(void) +{ + return static_branch(&__cfs_bandwidth_used); +} + +static void account_cfs_bandwidth_used(int enabled, int was_enabled) +{ + /* only need to count groups transitioning between enabled/!enabled */ + if (enabled && !was_enabled) + jump_label_inc(&__cfs_bandwidth_used); + else if (!enabled && was_enabled) + jump_label_dec(&__cfs_bandwidth_used); +} +#else /* !HAVE_JUMP_LABEL */ +/* static_branch doesn't help unless supported */ +static int cfs_bandwidth_used(void) +{ + return 1; +} +static void account_cfs_bandwidth_used(int enabled, int was_enabled) {} +#endif /* HAVE_JUMP_LABEL */ +#else /* !CONFIG_CFS_BANDWIDTH */ static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} @@ -9203,7 +9229,7 @@ static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime); static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) { - int i, ret = 0, runtime_enabled; + int i, ret = 0, runtime_enabled, runtime_was_enabled; struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); if (tg == &root_task_group) @@ -9231,6 +9257,9 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) goto out_unlock; runtime_enabled = quota != RUNTIME_INF; + runtime_was_enabled = cfs_b->quota != RUNTIME_INF; + account_cfs_bandwidth_used(runtime_enabled, runtime_was_enabled); + raw_spin_lock_irq(&cfs_b->lock); cfs_b->period = ns_to_ktime(period); cfs_b->quota = quota; |