[PATCH] trace/ftrace.c: remove redundant swap function

[PATCH] trace/ftrace.c: remove redundant swap function

[Rasmus Villemoes]

To cover the common case of sorting an array of pointers, Daniel
Wagner recently modified the library sort() to use a specific swap
function for size==8, in addition to the size==4 case which was
already handled. Since sizeof(long) is either 4 or 8,
ftrace_swap_ips() is redundant and we can just let sort() pick an
appropriate and fast swap callback.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
 kernel/trace/ftrace.c | 13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b0623ac785a2..186bafa9935d 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4783,17 +4783,6 @@ static int ftrace_cmp_ips(const void *a, const void *b)
 	return 0;
 }
 
-static void ftrace_swap_ips(void *a, void *b, int size)
-{
-	unsigned long *ipa = a;
-	unsigned long *ipb = b;
-	unsigned long t;
-
-	t = *ipa;
-	*ipa = *ipb;
-	*ipb = t;
-}
-
 static int ftrace_process_locs(struct module *mod,
 			       unsigned long *start,
 			       unsigned long *end)
@@ -4813,7 +4802,7 @@ static int ftrace_process_locs(struct module *mod,
 		return 0;
 
 	sort(start, count, sizeof(*start),
-	     ftrace_cmp_ips, ftrace_swap_ips);
+	     ftrace_cmp_ips, NULL);
 
 	start_pg = ftrace_allocate_pages(count);
 	if (!start_pg)
-- 
2.1.3

Re: [PATCH] trace/ftrace.c: remove redundant swap function

[Rasmus Villemoes]

On Wed, Sep 09 2015, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

ping

> To cover the common case of sorting an array of pointers, Daniel
> Wagner recently modified the library sort() to use a specific swap
> function for size==8, in addition to the size==4 case which was
> already handled. Since sizeof(long) is either 4 or 8,
> ftrace_swap_ips() is redundant and we can just let sort() pick an
> appropriate and fast swap callback.
>
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
>  kernel/trace/ftrace.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index b0623ac785a2..186bafa9935d 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -4783,17 +4783,6 @@ static int ftrace_cmp_ips(const void *a, const void *b)
>  	return 0;
>  }
>  
> -static void ftrace_swap_ips(void *a, void *b, int size)
> -{
> -	unsigned long *ipa = a;
> -	unsigned long *ipb = b;
> -	unsigned long t;
> -
> -	t = *ipa;
> -	*ipa = *ipb;
> -	*ipb = t;
> -}
> -
>  static int ftrace_process_locs(struct module *mod,
>  			       unsigned long *start,
>  			       unsigned long *end)
> @@ -4813,7 +4802,7 @@ static int ftrace_process_locs(struct module *mod,
>  		return 0;
>  
>  	sort(start, count, sizeof(*start),
> -	     ftrace_cmp_ips, ftrace_swap_ips);
> +	     ftrace_cmp_ips, NULL);
>  
>  	start_pg = ftrace_allocate_pages(count);
>  	if (!start_pg)

Re: [PATCH] trace/ftrace.c: remove redundant swap function

[Steven Rostedt]

On Wed, 30 Sep 2015 21:43:38 +0200
Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:

> On Wed, Sep 09 2015, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote:
> 
> ping

Both your patches look good. I applied both of them to my tree for the
4.4 window.

I'll post them to linux-next after they've gone through my test suite.
But currently my tests are running -rt code, and I may not get to them
till I get back from LinuxCon EU. But they are in the queue.

Thanks!

-- Steve


> 
> > To cover the common case of sorting an array of pointers, Daniel
> > Wagner recently modified the library sort() to use a specific swap
> > function for size==8, in addition to the size==4 case which was
> > already handled. Since sizeof(long) is either 4 or 8,
> > ftrace_swap_ips() is redundant and we can just let sort() pick an
> > appropriate and fast swap callback.
> >
> > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
>