From 09c72028392cf5e12532411c0a0caa72d886b6b6 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 5 Mar 2015 15:21:20 +0100 Subject: kernel/latencytop: Add non-scheduler interface for latency reporting Some sources of significant amounts of latency aren't simple sleeps but instead busy-loops or a series of hundreds of small sleeps simply because the hardware can't do better. Unfortunately latencytop doesn't register these and so they slip under the radar. Hence expose a simplified interface to report additional latencies and export the underlying function so that modules can use this. The example I have in mind are edid reads. The drm subsystem exposes both interfaces to do full probes and to just get at the cached state from the last probe and often userspace developers don't know about the difference and incur unecessary big latencies. And usually the i2c transfer is done with busy-looping or if there is a hw engine it might only be able to transfer a few bytes per sleep/irq cycle. And edid reads take at least 12ms and with crappy hw can easily be a few hundred ms. v2: Simplify #ifdefs a bit (Chris). Cc: Chris Wilson Cc: Thomas Gleixner Cc: Arjan van de Ven Cc: Andrew Morton Signed-off-by: Daniel Vetter --- kernel/latencytop.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel') diff --git a/kernel/latencytop.c b/kernel/latencytop.c index 781249098cb6..04cc0dff6550 100644 --- a/kernel/latencytop.c +++ b/kernel/latencytop.c @@ -63,6 +63,7 @@ static DEFINE_RAW_SPINLOCK(latency_lock); static struct latency_record latency_record[MAXLR]; int latencytop_enabled; +EXPORT_SYMBOL_GPL(latencytop_enabled); #ifdef CONFIG_SYSCTL static int sysctl_latencytop(struct ctl_table *table, int write, void *buffer, @@ -239,6 +240,7 @@ __account_scheduler_latency(struct task_struct *tsk, int usecs, int inter) out_unlock: raw_spin_unlock_irqrestore(&latency_lock, flags); } +EXPORT_SYMBOL_GPL(__account_scheduler_latency); static int lstats_show(struct seq_file *m, void *v) { -- cgit v1.2.3