| Message ID | 20180404205102.20816-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Can you add a patch on top. I already added your patch to my tree. See branch ftrace/core git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git -- Steve On April 4, 2018 4:51:02 PM EDT, Chris Wilson <chris@chris-wilson.co.uk> wrote: >Across suspend, we may see a very large drift in timestamps if the >sched >clock is unstable, prompting the global trace's ringbuffer code to warn >and suggest switching to the global clock. Preempt this request by >detecting when the sched clock is unstable (determined during >late_initcall) and automatically switching the default clock over to >trace_global_clock. > >This should prevent requiring user interaction to resolve warnings such >as: > >Delta way too big! 18446743856563626466 ts=18446744054496180323 write >stamp = 197932553857 > If you just came from a suspend/resume, > please switch to the trace global clock: > echo global > /sys/kernel/debug/tracing/trace_clock > >Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> >Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> >--- >v2: Tell the user what's happening and what they can do to correct it. >v3: Restore the correct logic to switch only if the default trace clock >(no override) is found to be *not* stable. >--- > kernel/trace/trace.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > >diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c >index 13baf85b27d8..a1810b053f65 100644 >--- a/kernel/trace/trace.c >+++ b/kernel/trace/trace.c >@@ -41,6 +41,7 @@ > #include <linux/nmi.h> > #include <linux/fs.h> > #include <linux/trace.h> >+#include <linux/sched/clock.h> > #include <linux/sched/rt.h> > > #include "trace.h" >@@ -8505,3 +8506,21 @@ __init static int clear_boot_tracer(void) > > fs_initcall(tracer_init_tracefs); > late_initcall_sync(clear_boot_tracer); >+ >+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK >+__init static int tracing_set_default_clock(void) >+{ >+ /* sched_clock_stable() is determined in late_initcall */ >+ if (!trace_boot_clock && !sched_clock_stable()) { >+ printk(KERN_WARNING >+ "Unstable clock detected, switching default tracing clock to >\"global\"\n" >+ "If you want to keep using the local clock, then add:\n" >+ " \"trace_clock=local\"\n" >+ "on the kernel command line\n"); >+ tracing_set_clock(&global_trace, "global"); >+ } >+ >+ return 0; >+} >+late_initcall_sync(tracing_set_default_clock); >+#endif
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 13baf85b27d8..a1810b053f65 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -41,6 +41,7 @@ #include <linux/nmi.h> #include <linux/fs.h> #include <linux/trace.h> +#include <linux/sched/clock.h> #include <linux/sched/rt.h> #include "trace.h" @@ -8505,3 +8506,21 @@ __init static int clear_boot_tracer(void) fs_initcall(tracer_init_tracefs); late_initcall_sync(clear_boot_tracer); + +#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK +__init static int tracing_set_default_clock(void) +{ + /* sched_clock_stable() is determined in late_initcall */ + if (!trace_boot_clock && !sched_clock_stable()) { + printk(KERN_WARNING + "Unstable clock detected, switching default tracing clock to \"global\"\n" + "If you want to keep using the local clock, then add:\n" + " \"trace_clock=local\"\n" + "on the kernel command line\n"); + tracing_set_clock(&global_trace, "global"); + } + + return 0; +} +late_initcall_sync(tracing_set_default_clock); +#endif
Across suspend, we may see a very large drift in timestamps if the sched clock is unstable, prompting the global trace's ringbuffer code to warn and suggest switching to the global clock. Preempt this request by detecting when the sched clock is unstable (determined during late_initcall) and automatically switching the default clock over to trace_global_clock. This should prevent requiring user interaction to resolve warnings such as: Delta way too big! 18446743856563626466 ts=18446744054496180323 write stamp = 197932553857 If you just came from a suspend/resume, please switch to the trace global clock: echo global > /sys/kernel/debug/tracing/trace_clock Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Steven Rostedt (VMware) <rostedt@goodmis.org> --- v2: Tell the user what's happening and what they can do to correct it. v3: Restore the correct logic to switch only if the default trace clock (no override) is found to be *not* stable. --- kernel/trace/trace.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)