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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