[lustre-devel] [PATCH 11/21] lustre: cl_object: remove vestigial debugging.

[NeilBrown <neilb@suse.com>]

On Tue, Feb 12 2019, James Simmons wrote:

>> >> cl_env_inc() and cl_env_dec() don't do anything,
>> >> so discard them.
>> >
>> > I don't know about this one. I saw Andreas response as well. 
>> > So this was apart of "LU-744 obdclass: revise stats for cl_object cache"
>> > In the end it was turned off by default in the OpenSFS branch since it
>> > made performance take a hit. To enable in OpenSFS branch you have to run
>> > ./configure --enable-pgstate-track. We have a few like this for Lustre so
>> > I was going to bring this up. Do we want to remove this work for both the
>> > upstream client as well as OpenSFS tree or properly implement this by
>> > making it a Kconfig option when CONFIG_LUSTRE_DEBUG_EXPENSIVE_CHECK is
>> > enabled? Its just a matter of porting OpenSFS commit 
>> > 5cae09a2409dcd396a1ee7be1eca7d3bbf77365e
>> >
>> > What do you think?
>> 
>> How useful are these stats?
>> Stats that are never compiled in aren't likely to tell you much :-)
>> 
>> Has any thought been given to per-cpu stats counting?  That seems to be
>> the preferred approach for high-frequency accounting.
>> 
>> I think having a CONFIG option to enable expensive consistency checks is
>> a good idea - developers will enable it when they don't care about
>> performance.
>> Having a CONFIG option for expensive performance stats seems... weird.
>> Who would use it, and how meaningful would the number be?
>
> Which per-cpu stats are you talking about?

include/linux/percpu_counter.h I guess - or something similar.

NeilBrown



>                                             I know perf can do this kind of
> profiling with performance counters but I don't think you can use those
> with cl_pages specifically. I know the lustre developers really dislike
> trace point but this could be one of those cases where it makes sense.
>  
>> NeilBrown
>> 
>> 
>> >
>> >> Signed-off-by: NeilBrown <neilb@suse.com>
>> >> ---
>> >>  drivers/staging/lustre/lustre/obdclass/cl_object.c |   15 ---------------
>> >>  1 file changed, 15 deletions(-)
>> >> 
>> >> diff --git a/drivers/staging/lustre/lustre/obdclass/cl_object.c b/drivers/staging/lustre/lustre/obdclass/cl_object.c
>> >> index d71a680660da..1e704078664e 100644
>> >> --- a/drivers/staging/lustre/lustre/obdclass/cl_object.c
>> >> +++ b/drivers/staging/lustre/lustre/obdclass/cl_object.c
>> >> @@ -565,14 +565,6 @@ struct cl_env {
>> >>  	void		       *ce_debug;
>> >>  };
>> >>  
>> >> -static void cl_env_inc(enum cache_stats_item item)
>> >> -{
>> >> -}
>> >> -
>> >> -static void cl_env_dec(enum cache_stats_item item)
>> >> -{
>> >> -}
>> >> -
>> >>  static void cl_env_init0(struct cl_env *cle, void *debug)
>> >>  {
>> >>  	LASSERT(cle->ce_ref == 0);
>> >> @@ -581,7 +573,6 @@ static void cl_env_init0(struct cl_env *cle, void *debug)
>> >>  
>> >>  	cle->ce_ref = 1;
>> >>  	cle->ce_debug = debug;
>> >> -	cl_env_inc(CS_busy);
>> >>  }
>> >>  
>> >>  static struct lu_env *cl_env_new(u32 ctx_tags, u32 ses_tags, void *debug)
>> >> @@ -611,9 +602,6 @@ static struct lu_env *cl_env_new(u32 ctx_tags, u32 ses_tags, void *debug)
>> >>  		if (rc != 0) {
>> >>  			kmem_cache_free(cl_env_kmem, cle);
>> >>  			env = ERR_PTR(rc);
>> >> -		} else {
>> >> -			cl_env_inc(CS_create);
>> >> -			cl_env_inc(CS_total);
>> >>  		}
>> >>  	} else {
>> >>  		env = ERR_PTR(-ENOMEM);
>> >> @@ -623,7 +611,6 @@ static struct lu_env *cl_env_new(u32 ctx_tags, u32 ses_tags, void *debug)
>> >>  
>> >>  static void cl_env_fini(struct cl_env *cle)
>> >>  {
>> >> -	cl_env_dec(CS_total);
>> >>  	lu_context_fini(&cle->ce_lu.le_ctx);
>> >>  	lu_context_fini(&cle->ce_ses);
>> >>  	kmem_cache_free(cl_env_kmem, cle);
>> >> @@ -782,7 +769,6 @@ void cl_env_put(struct lu_env *env, u16 *refcheck)
>> >>  	if (--cle->ce_ref == 0) {
>> >>  		int cpu = get_cpu();
>> >>  
>> >> -		cl_env_dec(CS_busy);
>> >>  		cle->ce_debug = NULL;
>> >>  		cl_env_exit(cle);
>> >>  		/*
>> >> @@ -903,7 +889,6 @@ void cl_env_percpu_put(struct lu_env *env)
>> >>  	cle->ce_ref--;
>> >>  	LASSERT(cle->ce_ref == 0);
>> >>  
>> >> -	cl_env_dec(CS_busy);
>> >>  	cle->ce_debug = NULL;
>> >>  
>> >>  	put_cpu();
>> >> 
>> >> 
>> >> 
>> 
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