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

From: Mathieu Poirier <[email-masked]>
Date: Fri, 11 Oct 2019 13:59:28 -0600

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 <[email-masked]>
> ---
>  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
> 

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