Re: [PATCH] Scheduler Profiling - Use Immediate Values

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

Hi Randy,

* Randy Dunlap (randy.dunlap@oracle.com) wrote:
> On Thu, 6 Sep 2007 16:05:37 -0400 Mathieu Desnoyers wrote:
> 
> > Scheduler Profiling - Use Immediate Values
> > 
> > Use immediate values with lower d-cache hit in optimized version as a
> > condition for scheduler profiling call.
> > 
> > Depends on the Immediate values patches, applies to 2.6.23-rc4-mm1.
> > 
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> > ---
> >  drivers/kvm/svm.c       |    2 +-
> >  drivers/kvm/vmx.c       |    2 +-
> >  include/linux/profile.h |   10 ++++------
> >  kernel/profile.c        |   38 ++++++++++++++++++++++++++------------
> >  kernel/sched.c          |    3 ++-
> >  5 files changed, 34 insertions(+), 21 deletions(-)
> > 
> > Index: linux-2.6-lttng/kernel/profile.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/kernel/profile.c	2007-09-04 11:53:23.000000000 -0400
> > +++ linux-2.6-lttng/kernel/profile.c	2007-09-04 12:12:16.000000000 -0400
> > @@ -42,9 +42,6 @@ static int (*timer_hook)(struct pt_regs 
> >  static atomic_t *prof_buffer;
> >  static unsigned long prof_len, prof_shift;
> >  
> > -int prof_on __read_mostly;
> > -EXPORT_SYMBOL_GPL(prof_on);
> > -
> >  static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
> >  #ifdef CONFIG_SMP
> >  static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
> > @@ -52,6 +49,14 @@ static DEFINE_PER_CPU(int, cpu_profile_f
> >  static DEFINE_MUTEX(profile_flip_mutex);
> >  #endif /* CONFIG_SMP */
> >  
> > +/* Immediate values */
> > +immediate_char_t sleep_profiling __read_mostly,
> > +			sched_profiling __read_mostly,
> > +			kvm_profiling __read_mostly,
> > +			cpu_profiling __read_mostly;
> > +EXPORT_SYMBOL_GPL(kvm_profiling);
> > +EXPORT_SYMBOL_GPL(cpu_profiling);
> > +
> >  static int __init profile_setup(char * str)
> >  {
> >  	static char __initdata schedstr[] = "schedule";
> > @@ -60,7 +65,7 @@ static int __init profile_setup(char * s
> >  	int par;
> >  
> >  	if (!strncmp(str, sleepstr, strlen(sleepstr))) {
> > -		prof_on = SLEEP_PROFILING;
> > +		immediate_set_early(&sleep_profiling, 1);
> 
> These are booleans, eh?  so one could use            , true);
> 
> etc.
> 
> >  		if (str[strlen(sleepstr)] == ',')
> >  			str += strlen(sleepstr) + 1;
> >  		if (get_option(&str, &par))
> > @@ -99,7 +104,10 @@ __setup("profile=", profile_setup);
> >  
> >  void __init profile_init(void)
> >  {
> > -	if (!prof_on) 
> > +	if (!_immediate_read(&sleep_profiling) &&
> > +		!_immediate_read(&sched_profiling) &&
> > +		!_immediate_read(&kvm_profiling) &&
> > +		!_immediate_read(&cpu_profiling))
> 
> Looks like this (in multiple places) needs to use prof_on, where
> prof_on is set earlier as the logical 'or' of all (4 now, could be more)
> profiling flags.

I first did this patch when the immediate values only supported
booleans. I just redid it encoding the original prof_on values in a
signle immediate_char_t variable. It makes the change must less
intrusive.

Since there seem to be only one type of profiling possible at a given
time, there is no need for a bitfield : just doing the same as prof_on
currently does seems ok.

> Or below, sometimes you just check prof_buffer.  Is that sufficient
> here also?
> 

Yes, before we already do the check early in profile_hit (inline
function checking the same condition). In this patch, I moved the check
out of profile_hit, but since I now re-use prof_on with values, I can
put it back in profile_hit().

> >  		return;
> >   
> >  	/* only text is profiled */
> > @@ -288,7 +296,7 @@ void profile_hits(int type, void *__pc, 
> >  	int i, j, cpu;
> >  	struct profile_hit *hits;
> >  
> > -	if (prof_on != type || !prof_buffer)
> > +	if (!prof_buffer)
> >  		return;
> >  	pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
> >  	i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
> > @@ -398,7 +406,7 @@ void profile_hits(int type, void *__pc, 
> >  {
> >  	unsigned long pc;
> >  
> > -	if (prof_on != type || !prof_buffer)
> > +	if (!prof_buffer)
> >  		return;
> >  	pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
> >  	atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
> > @@ -555,7 +563,10 @@ static int __init create_hash_tables(voi
> >  	}
> >  	return 0;
> >  out_cleanup:
> > -	prof_on = 0;
> > +	immediate_set_early(&sleep_profiling, 0);
> > +	immediate_set_early(&sched_profiling, 0);
> > +	immediate_set_early(&kvm_profiling, 0);
> > +	immediate_set_early(&cpu_profiling, 0);
> >  	smp_mb();
> >  	on_each_cpu(profile_nop, NULL, 0, 1);
> >  	for_each_online_cpu(cpu) {
> > @@ -582,7 +593,10 @@ static int __init create_proc_profile(vo
> >  {
> >  	struct proc_dir_entry *entry;
> >  
> > -	if (!prof_on)
> > +	if (!_immediate_read(&sleep_profiling) &&
> > +		!_immediate_read(&sched_profiling) &&
> > +		!_immediate_read(&kvm_profiling) &&
> > +		!_immediate_read(&cpu_profiling))
> >  		return 0;
> >  	if (create_hash_tables())
> >  		return -1;
> 
> 
> ---
> ~Randy
> *** Remember to use Documentation/SubmitChecklist when testing your code ***

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68