Re: perf/tracepoints access to interpreted strings

From: David Ahern
Date: Mon Apr 20 2015 - 17:27:04 EST


On 4/20/15 3:25 PM, Arnaldo Carvalho de Melo wrote:
Em Mon, Apr 20, 2015 at 04:46:16PM -0400, Steven Rostedt escreveu:
On Wed, 15 Apr 2015 15:09:27 -0300
Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
If it is strictly an enum, i.e. no holes and just by looking at the
"format" file above I don't see how it could have holes, albeit enums
may have, we can as well have this:

const char *perf_evsel__enum(struct perf_evsel *evsel,
struct perf_sample *sample,
const char *enum_name);

That would return an array of strings that you could directly access,
indexing using some of the fields.

I.e. internally we would see the tracepoint format file as:

field:enum action vec; offset:12; size:4; signed:0;

enum: action: TIMER, NET_TX, NET_RX, BLOCK, BLOCK_IOPOLL, TASKLET, SCHED, HRTIMER, RCU

Note, with the new TRACE_DEFINE_ENUM() that was already added to
Linus's tree, that print_fmt now looks like:

print fmt: "vec=%u [action=%s]", REC->vec, __print_symbolic(REC->vec,
{ 0, "HI" }, { 1, "TIMER" }, { 2, "NET_TX" }, { 3, "NET_RX" }, { 4, "BLOCK" },
{ 5, "BLOCK_IOPOLL" }, { 6, "TASKLET" }, { 7, "SCHED" }, { 8, "HRTIMER" },
{ 9, "RCU" })

That is better, indeed, covers holes :-)

Seems to me that means 2 different implementations are needed ... old and new.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/