On Sun, Jun 12, 2016 at 10:22:01PM -0400, Steven Rostedt wrote:
On Sun, 12 Jun 2016 23:25:10 +0200 Henrik Austad henrik@austad.us wrote:
+#include <linux/if_ether.h> +#include <linux/if_vlan.h> +/* #include <linux/skbuff.h> */
+/* FIXME: update to TRACE_CLASS to reduce overhead */
I'm curious to why I didn't do this now. A class would make less duplication of typing too ;-)
Yeah, I found this in a really great article written by some tracing-dude, I hear he talks really, really fast!
I plead the 5th!
https://lwn.net/Articles/381064/
+TRACE_EVENT(tsn_buffer_write,
- TP_PROTO(struct tsn_link *link,
size_t bytes),- TP_ARGS(link, bytes),
- TP_STRUCT__entry(
__field(u64, stream_id)__field(size_t, size)__field(size_t, bsize)__field(size_t, size_left)__field(void *, buffer)__field(void *, head)__field(void *, tail)__field(void *, end)),- TP_fast_assign(
__entry->stream_id = link->stream_id;__entry->size = bytes;__entry->bsize = link->used_buffer_size;__entry->size_left = (link->head - link->tail) % link->used_buffer_size;Move this logic into the print statement, since you save head and tail.
Ok, any particular reason?
Because it removes calculations during the trace. The calculations done in TP_printk() are done at the time of reading the trace, and calculations done in TP_fast_assign() are done during the recording and hence adding more overhead to the trace itself.
Aha! that makes sense, thanks! (/me goes and updates the tracing-part)
-Henrik