[PATCH 1/1] perf diff: Use fabs instead of, ugh, casting to u64

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

To check which deltas should be printed. Things looks more believable now, I
guess:

$ perf report -i perf.data.old --sort dso,symbol | head -13
     9.02%  libc-2.10.1.so               [.] _IO_vfprintf_internal
     4.88%  find                         [.] 0x00000000014af0
     2.91%  [kernel]                     [k] __kmalloc
     2.85%  [kernel]                     [k] ext4_htree_store_dirent
     2.50%  libc-2.10.1.so               [.] __GI_memmove
     2.44%  [kernel]                     [k] half_md4_transform
     2.43%  [kernel]                     [k] _spin_lock
     2.33%  [kernel]                     [k] system_call
$ perf report -i perf.data --sort dso,symbol | head -13
     8.55%  libc-2.10.1.so               [.] _IO_vfprintf_internal
     3.11%  [kernel]                     [k] __kmalloc
     3.07%  [kernel]                     [k] ext4_htree_store_dirent
     2.66%  find                         [.] 0x00000000016bcf
     2.61%  [kernel]                     [k] _atomic_dec_and_lock
     2.46%  [kernel]                     [k] half_md4_transform
     2.41%  libc-2.10.1.so               [.] __GI_memmove
     2.30%  find                         [.] 0x00000000009219
$ perf diff | head -13
     9.02%     -0.47%  libc-2.10.1.so               [.] _IO_vfprintf_internal
     2.91%     +0.20%  [kernel]                     [k] __kmalloc
     2.85%     +0.23%  [kernel]                     [k] ext4_htree_store_dirent
     1.99%     +0.62%  [kernel]                     [k] _atomic_dec_and_lock
     2.44%     +0.02%  [kernel]                     [k] half_md4_transform
     2.50%     -0.09%  libc-2.10.1.so               [.] __GI_memmove
     1.88%     +0.01%  [kernel]                     [k] __d_lookup
     2.43%     -0.75%  [kernel]                     [k] _spin_lock
     0.97%     +0.62%  [kernel]                     [k] path_get
     1.99%     -0.42%  libc-2.10.1.so               [.] _int_malloc
$

Cc: FrÃdÃric Weisbecker <fweisbec@xxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/hist.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index 1bf8658..e8daf5c 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -1,6 +1,7 @@
 #include "hist.h"
 #include "session.h"
 #include "sort.h"
+#include <math.h>
 
 struct callchain_param	callchain_param = {
 	.mode	= CHAIN_GRAPH_REL,
@@ -498,9 +499,9 @@ static size_t hist_entry__fprintf(struct hist_entry *self,
 		if (session->events_stats.total > 0)
 			new_percent = (self->count * 100.0) / session->events_stats.total;
 
-		diff = old_percent - new_percent;
+		diff = new_percent - old_percent;
 
-		if ((u64)diff != 0)
+		if (fabs(diff) >= 0.01)
 			snprintf(bf, sizeof(bf), "%+4.2F%%", diff);
 		else
 			snprintf(bf, sizeof(bf), " ");
-- 
1.6.2.5

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