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Date: Tue, 10 Mar 2020 12:11:17 -0300
From: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To: Jin Yao <yao.jin@...ux.intel.com>
Cc: jolsa@...nel.org, peterz@...radead.org, mingo@...hat.com,
alexander.shishkin@...ux.intel.com, Linux-kernel@...r.kernel.org,
ak@...ux.intel.com, kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v1 02/14] perf util: Create streams for managing top N
hottest callchains
Em Tue, Mar 10, 2020 at 03:02:33PM +0800, Jin Yao escreveu:
> We think the stream is a callchain which is aggregated by the LBR
> records from samples. By browsing the stream, we can understand
> the code flow.
>
> The struct callchain_node represents one callchain and we use the
> callchain_node->hit to measure the hot level of this callchain.
> Higher is hotter.
>
> Since in perf data file, there may be many callchains so we just
> need to focus on the top N hottest callchains. N is a user defined
> parameter or just a predefined default value.
>
> This patch saves the top N hottest callchains in 'struct stream_node'
> type array, which is defined in a per event 'struct callchain_streams'.
>
> So now we can get the per-event top N hottest callchains.
>
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
> tools/perf/util/callchain.c | 125 ++++++++++++++++++++++++++++++++++++
> tools/perf/util/callchain.h | 16 +++++
> 2 files changed, 141 insertions(+)
>
> diff --git a/tools/perf/util/callchain.c b/tools/perf/util/callchain.c
> index 818aa4efd386..d9c68a8e7619 100644
> --- a/tools/perf/util/callchain.c
> +++ b/tools/perf/util/callchain.c
> @@ -31,6 +31,7 @@
> #include "callchain.h"
> #include "branch.h"
> #include "symbol.h"
> +#include "evlist.h"
> #include "../perf.h"
>
> #define CALLCHAIN_PARAM_DEFAULT \
> @@ -1599,3 +1600,127 @@ void callchain_cursor_reset(struct callchain_cursor *cursor)
> for (node = cursor->first; node != NULL; node = node->next)
> map__zput(node->ms.map);
> }
> +
> +static void free_evsel_streams(struct callchain_streams *callchain_streams,
> + int nr_evsel)
> +{
> + for (int i = 0; i < nr_evsel; i++) {
> + if (callchain_streams[i].streams)
> + free(callchain_streams[i].streams);
free(NULL) is valid, so remove that extra check and use zfree() to reset
that entry to NULL, i.e.:
for ()
zfree(&callchain_streams[i].streams);
> + }
> +
> + free(callchain_streams);
> +}
> +
> +static struct callchain_streams *create_evsel_streams(int nr_evsel,
> + int nr_streams_max)
> +{
> + struct callchain_streams *callchain_streams;
> +
> + callchain_streams = calloc(nr_evsel, sizeof(struct callchain_streams));
calloc is the right thing here, as this is an array
> + if (!callchain_streams)
> + return NULL;
> +
> + for (int i = 0; i < nr_evsel; i++) {
> + struct callchain_streams *s = &callchain_streams[i];
> +
> + s->streams = calloc(nr_streams_max, sizeof(struct stream_node));
> + if (!s->streams)
> + goto err;
> +
> + s->nr_streams_max = nr_streams_max;
> + s->evsel_idx = -1;
> + }
> +
> + return callchain_streams;
> +
> +err:
> + free_evsel_streams(callchain_streams, nr_evsel);
> + return NULL;
> +}
> +
> +/*
> + * The cnodes with high hit number are hot callchains.
> + */
> +static void set_hot_cnode(struct callchain_streams *s,
> + struct callchain_node *cnode)
> +{
> + int i, idx = 0;
> + u64 hit;
> +
> + if (s->nr_streams < s->nr_streams_max) {
> + i = s->nr_streams;
> + s->streams[i].cnode = cnode;
> + s->nr_streams++;
> + return;
> + }
> +
> + /*
> + * Since only a few number of hot streams, so only use simple
> + * way to find the cnode with smallest hit number and replace.
> + */
> + hit = (s->streams[0].cnode)->hit;
> + for (i = 1; i < s->nr_streams; i++) {
> + if ((s->streams[i].cnode)->hit < hit) {
> + hit = (s->streams[i].cnode)->hit;
> + idx = i;
> + }
> + }
> +
> + if (cnode->hit > hit)
> + s->streams[idx].cnode = cnode;
> +}
> +
> +static void update_hot_streams(struct hist_entry *he,
> + struct callchain_streams *s)
> +{
> + struct rb_root *root = &he->sorted_chain;
> + struct rb_node *rb_node = rb_first(root);
> + struct callchain_node *node;
> +
> + while (rb_node) {
> + node = rb_entry(rb_node, struct callchain_node, rb_node);
> + set_hot_cnode(s, node);
> + rb_node = rb_next(rb_node);
> + }
> +}
> +
> +static void get_hot_streams(struct hists *hists,
> + struct callchain_streams *s)
> +{
> + struct rb_node *next;
> +
> + next = rb_first_cached(&hists->entries);
> + while (next) {
> + struct hist_entry *he;
> +
> + he = rb_entry(next, struct hist_entry, rb_node);
> + update_hot_streams(he, s);
> + next = rb_next(&he->rb_node);
> + }
> +}
> +
> +struct callchain_streams *callchain_evsel_streams_create(struct evlist *evlist,
> + int nr_streams_max,
> + int *nr_evsel_streams)
> +{
> + int nr_evsel = evlist->core.nr_entries, i = 0;
> + struct callchain_streams *callchain_streams;
> + struct evsel *pos;
> +
> + callchain_streams = create_evsel_streams(nr_evsel, nr_streams_max);
> + if (!callchain_streams)
> + return NULL;
> +
> + evlist__for_each_entry(evlist, pos) {
> + struct hists *hists = evsel__hists(pos);
> +
> + hists__output_resort(hists, NULL);
> + get_hot_streams(hists, &callchain_streams[i]);
> + callchain_streams[i].evsel_idx = pos->idx;
> + i++;
> + }
> +
> + *nr_evsel_streams = nr_evsel;
> + return callchain_streams;
> +}
> diff --git a/tools/perf/util/callchain.h b/tools/perf/util/callchain.h
> index 706bb7bbe1e1..5852990cdf60 100644
> --- a/tools/perf/util/callchain.h
> +++ b/tools/perf/util/callchain.h
> @@ -13,6 +13,7 @@ struct ip_callchain;
> struct map;
> struct perf_sample;
> struct thread;
> +struct evlist;
>
> #define HELP_PAD "\t\t\t\t"
>
> @@ -159,6 +160,17 @@ struct callchain_cursor {
> struct callchain_cursor_node *curr;
> };
>
> +struct stream_node {
> + struct callchain_node *cnode;
> +};
> +
> +struct callchain_streams {
> + struct stream_node *streams;
> + int nr_streams_max;
> + int nr_streams;
> + int evsel_idx;
> +};
> +
> extern __thread struct callchain_cursor callchain_cursor;
>
> static inline void callchain_init(struct callchain_root *root)
> @@ -289,4 +301,8 @@ int callchain_branch_counts(struct callchain_root *root,
> u64 *branch_count, u64 *predicted_count,
> u64 *abort_count, u64 *cycles_count);
>
> +struct callchain_streams *callchain_evsel_streams_create(struct evlist *evlist,
> + int nr_streams_max,
> + int *nr_evsel_streams);
> +
> #endif /* __PERF_CALLCHAIN_H */
> --
> 2.17.1
>
--
- Arnaldo
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