Re: [PATCH V2 2/7] mm/gup: add gup trace points

[Shi, Yang]

On 12/2/2015 3:36 PM, Dave Hansen wrote:
> On 12/02/2015 02:53 PM, Yang Shi wrote:
> > diff --git a/mm/gup.c b/mm/gup.c
> > index deafa2c..10245a4 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -13,6 +13,9 @@
> >   #include <linux/rwsem.h>
> >   #include <linux/hugetlb.h>
> >
> > +#define CREATE_TRACE_POINTS
> > +#include <trace/events/gup.h>
> > +
> >   #include <asm/pgtable.h>
> >   #include <asm/tlbflush.h>
>
> This needs to be _the_ last thing that gets #included.  Otherwise, you
> risk colliding with any other trace header that gets implicitly included
> below.

Thanks for the suggestion, will move it to the last.

> > @@ -1340,6 +1346,8 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
> >   					start, len)))
> >   		return 0;
> >
> > +	trace_gup_get_user_pages_fast(start, nr_pages, write, pages);
> > +
> >   	/*
> >   	 * Disable interrupts.  We use the nested form as we can already have
> >   	 * interrupts disabled by get_futex_key.
>
> It would be _really_ nice to be able to see return values from the
> various gup calls as well.  Is that feasible?

I think it should be feasible. kmem_cache_alloc trace event could show 
return value. I'm supposed gup trace events should be able to do the 
same thing.

Regards,
Yang

>

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