Re: [PATCH v3 5/6] perf cs-etm: Support callchain for instruction sample

From: Mathieu Poirier
Date: Fri Oct 11 2019 - 15:59:34 EST

On Sat, Oct 05, 2019 at 05:16:13PM +0800, Leo Yan wrote:
> Now CoreSight has supported the thread stack; based on the thread stack
> we can synthesize call chain for the instruction sample; the call chain
> can be injected by option '--itrace=g'.
>
> Before:
>
> # perf script --itrace=g16l64i100
> main 1579 100 instructions: ffff0000102137f0 group_sched_in+0xb0 ([kernel.kallsyms])
> main 1579 100 instructions: ffff000010213b78 flexible_sched_in+0xf0 ([kernel.kallsyms])
> main 1579 100 instructions: ffff0000102135ac event_sched_in.isra.57+0x74 ([kernel.kallsyms])
> main 1579 100 instructions: ffff000010219344 perf_swevent_add+0x6c ([kernel.kallsyms])
> main 1579 100 instructions: ffff000010214854 perf_event_update_userpage+0x4c ([kernel.kallsyms])
> [...]
>
> After:
>
> # perf script --itrace=g16l64i100
>
> main 1579 100 instructions:
> ffff000010213b78 flexible_sched_in+0xf0 ([kernel.kallsyms])
> ffff00001020c0b4 visit_groups_merge+0x12c ([kernel.kallsyms])
>
> main 1579 100 instructions:
> ffff0000102135ac event_sched_in.isra.57+0x74 ([kernel.kallsyms])
> ffff0000102137a0 group_sched_in+0x60 ([kernel.kallsyms])
> ffff000010213b84 flexible_sched_in+0xfc ([kernel.kallsyms])
> ffff00001020c0b4 visit_groups_merge+0x12c ([kernel.kallsyms])
>
> main 1579 100 instructions:
> ffff000010219344 perf_swevent_add+0x6c ([kernel.kallsyms])
> ffff0000102135f4 event_sched_in.isra.57+0xbc ([kernel.kallsyms])
> ffff0000102137a0 group_sched_in+0x60 ([kernel.kallsyms])
> ffff000010213b84 flexible_sched_in+0xfc ([kernel.kallsyms])
> ffff00001020c0b4 visit_groups_merge+0x12c ([kernel.kallsyms])
> [...]
>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
> tools/perf/util/cs-etm.c | 35 +++++++++++++++++++++++++++++++++--
> 1 file changed, 33 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 4b42f9c9bd34..56e501cd2f5f 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"
> @@ -74,6 +75,7 @@ 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;
> @@ -251,6 +253,16 @@ 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);
>
> @@ -275,6 +287,7 @@ 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);

Theoretically this should go two lines up, i.e just below
zfree(&tidq->prev_packet). If you agree with the comment I did in 3/6 then it
is worth doing the above change, otherwise it can stay that way.

> out:
> return rc;
> }
> @@ -546,6 +559,7 @@ 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);

Same comment as above. The rest looks good to me.

Mathieu

> zfree(&tidq);
>
> /*
> @@ -1126,7 +1140,7 @@ static void cs_etm__add_stack_event(struct cs_etm_queue *etmq,
> int insn_len;
> u64 from_ip, to_ip;
>
> - if (etm->synth_opts.thread_stack) {
> + 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);
>
> @@ -1182,6 +1196,14 @@ 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;
> @@ -1369,6 +1391,8 @@ 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;
>
> @@ -2639,7 +2663,6 @@ 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;
> }
> @@ -2651,6 +2674,14 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
> etm->branches_filter |= PERF_IP_FLAG_RETURN |
> PERF_IP_FLAG_TRACE_BEGIN;
>
> + 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);
> if (err)
> goto err_delete_thread;
> --
> 2.17.1
>