On Sun, Jun 12, 2016 at 10:22:01PM -0400, Steven Rostedt wrote: > On Sun, 12 Jun 2016 23:25:10 +0200 > Henrik Austad <hen...@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
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