From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Move the unsigned long long trace_id out from between the boolean
sync_enable and the int ts_samples_count, which removes the gap in the
structure, making the structure size drop from 32 bytes to 24, as displayed
by pahole.
Before:
struct host_trace_info {
_Bool sync_enable; /* 0 1 */
/* XXX 7 bytes hole, try to pack */
long long unsigned int trace_id; /* 8 8 */
int ts_samples_count; /* 16 4 */
/* XXX 4 bytes hole, try to pack */
struct ts_offset_sample * ts_samples; /* 24 8 */
/* size: 32, cachelines: 1, members: 4 */
/* sum members: 21, holes: 2, sum holes: 11 */
/* last cacheline: 32 bytes */
};
After:
struct host_trace_info {
long long unsigned int trace_id; /* 0 8 */
_Bool sync_enable; /* 8 1 */
/* XXX 3 bytes hole, try to pack */
int ts_samples_count; /* 12 4 */
struct ts_offset_sample * ts_samples; /* 16 8 */
/* size: 24, cachelines: 1, members: 4 */
/* sum members: 21, holes: 1, sum holes: 3 */
/* last cacheline: 24 bytes */
};
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
This is why I'm picky on ordering of fields in data structures.
I'm sure there's many more places we can update here.
-- Steve
lib/trace-cmd/trace-input.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index 2f0274d9..a1241f4b 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -83,8 +83,8 @@ struct ts_offset_sample {
};
struct host_trace_info {
- bool sync_enable;
unsigned long long trace_id;
+ bool sync_enable;
int ts_samples_count;
struct ts_offset_sample *ts_samples;
};
--
2.20.1
|