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Message-ID: <20190903220723.GC25787@xps15>
Date: Tue, 3 Sep 2019 16:07:23 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Leo Yan <leo.yan@...aro.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Suzuki K Poulose <suzuki.poulose@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Mike Leach <mike.leach@...aro.org>,
Robert Walker <Robert.Walker@....com>,
Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH v1 2/3] perf cs-etm: Add callchain to instruction sample
On Fri, Aug 30, 2019 at 02:24:20PM +0800, Leo Yan wrote:
> Firstly, this patch adds support for the thread stack; when every branch
> packet is coming we will push or pop the stack based on the sample
> flags.
>
> Secondly, based on the thread stack we can synthesize call chain for the
> instruction sample, this can be used by itrace option '--itrace=g'.
>
In most cases using the word "secondly" is a good indication the patch should be
split.
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
> tools/perf/util/cs-etm.c | 74 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 73 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 882a0718033d..ad573d3bd305 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -17,6 +17,7 @@
> #include <stdlib.h>
>
> #include "auxtrace.h"
> +#include "callchain.h"
> #include "color.h"
> #include "cs-etm.h"
> #include "cs-etm-decoder/cs-etm-decoder.h"
> @@ -69,6 +70,7 @@ struct cs_etm_traceid_queue {
> size_t last_branch_pos;
> union perf_event *event_buf;
> struct thread *thread;
> + struct ip_callchain *chain;
> struct branch_stack *last_branch;
> struct branch_stack *last_branch_rb;
> struct cs_etm_packet *prev_packet;
> @@ -246,6 +248,16 @@ static int cs_etm__init_traceid_queue(struct cs_etm_queue *etmq,
> if (!tidq->prev_packet)
> goto out_free;
>
> + if (etm->synth_opts.callchain) {
> + size_t sz = sizeof(struct ip_callchain);
> +
> + /* Add 1 to callchain_sz for callchain context */
> + sz += (etm->synth_opts.callchain_sz + 1) * sizeof(u64);
> + tidq->chain = zalloc(sz);
> + if (!tidq->chain)
> + goto out_free;
> + }
> +
> if (etm->synth_opts.last_branch) {
> size_t sz = sizeof(struct branch_stack);
>
> @@ -270,6 +282,7 @@ static int cs_etm__init_traceid_queue(struct cs_etm_queue *etmq,
> zfree(&tidq->last_branch);
> zfree(&tidq->prev_packet);
> zfree(&tidq->packet);
> + zfree(&tidq->chain);
> out:
> return rc;
> }
> @@ -541,6 +554,7 @@ static void cs_etm__free_traceid_queues(struct cs_etm_queue *etmq)
> zfree(&tidq->last_branch_rb);
> zfree(&tidq->prev_packet);
> zfree(&tidq->packet);
> + zfree(&tidq->chain);
> zfree(&tidq);
>
> /*
> @@ -1121,6 +1135,41 @@ static void cs_etm__copy_insn(struct cs_etm_queue *etmq,
> sample->insn_len, (void *)sample->insn);
> }
>
> +static void cs_etm__add_stack_event(struct cs_etm_queue *etmq,
> + struct cs_etm_traceid_queue *tidq)
> +{
> + struct cs_etm_auxtrace *etm = etmq->etm;
> + u8 trace_chan_id = tidq->trace_chan_id;
> + int insn_len;
> + u64 from_ip, to_ip;
> +
> + if (etm->synth_opts.callchain || etm->synth_opts.thread_stack) {
> +
> + from_ip = cs_etm__last_executed_instr(tidq->prev_packet);
> + to_ip = cs_etm__first_executed_instr(tidq->packet);
> +
> + /*
> + * T32 instruction size might be 32-bit or 16-bit, decide by
> + * calling cs_etm__t32_instr_size().
> + */
> + if (tidq->prev_packet->isa == CS_ETM_ISA_T32)
> + insn_len = cs_etm__t32_instr_size(etmq, trace_chan_id,
> + from_ip);
> + /* Otherwise, A64 and A32 instruction size are always 32-bit. */
> + else
> + insn_len = 4;
> +
> + thread_stack__event(tidq->thread, tidq->prev_packet->cpu,
> + tidq->prev_packet->flags,
> + from_ip, to_ip, insn_len,
> + etmq->buffer->buffer_nr);
> + } else {
> + thread_stack__set_trace_nr(tidq->thread,
> + tidq->prev_packet->cpu,
> + etmq->buffer->buffer_nr);
Please add a comment on what the above does. As a rule of thumb I add a comment
per addition in a patch in order to help people understand what is happening and
some of the reasonning behing the code.
> + }
> +}
> +
> static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq,
> struct cs_etm_traceid_queue *tidq,
> u64 addr, u64 period)
> @@ -1146,6 +1195,14 @@ static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq,
>
> cs_etm__copy_insn(etmq, tidq->trace_chan_id, tidq->packet, &sample);
>
> + if (etm->synth_opts.callchain) {
> + thread_stack__sample(tidq->thread, tidq->packet->cpu,
> + tidq->chain,
> + etm->synth_opts.callchain_sz + 1,
> + sample.ip, etm->kernel_start);
> + sample.callchain = tidq->chain;
> + }
> +
> if (etm->synth_opts.last_branch) {
> cs_etm__copy_last_branch_rb(etmq, tidq);
> sample.branch_stack = tidq->last_branch;
> @@ -1329,6 +1386,8 @@ static int cs_etm__synth_events(struct cs_etm_auxtrace *etm,
> attr.sample_type &= ~(u64)PERF_SAMPLE_ADDR;
> }
>
> + if (etm->synth_opts.callchain)
> + attr.sample_type |= PERF_SAMPLE_CALLCHAIN;
> if (etm->synth_opts.last_branch)
> attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
>
> @@ -1397,6 +1456,9 @@ static int cs_etm__sample(struct cs_etm_queue *etmq,
> tidq->period_instructions = instrs_over;
> }
>
> + if (tidq->prev_packet->last_instr_taken_branch)
> + cs_etm__add_stack_event(etmq, tidq);
> +
> if (etm->sample_branches) {
> bool generate_sample = false;
>
> @@ -2596,7 +2658,17 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
> } else {
> itrace_synth_opts__set_default(&etm->synth_opts,
> session->itrace_synth_opts->default_no_sample);
> - etm->synth_opts.callchain = false;
> +
> + etm->synth_opts.thread_stack =
> + session->itrace_synth_opts->thread_stack;
> + }
> +
> + if (etm->synth_opts.callchain && !symbol_conf.use_callchain) {
> + symbol_conf.use_callchain = true;
> + if (callchain_register_param(&callchain_param) < 0) {
> + symbol_conf.use_callchain = false;
> + etm->synth_opts.callchain = false;
> + }
> }
>
> err = cs_etm__synth_events(etm, session);
> --
> 2.17.1
>
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