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Date: Wed, 11 Mar 2020 13:38:37 +0800
From: "Jin, Yao" <yao.jin@...ux.intel.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.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
On 3/10/2020 11:11 PM, Arnaldo Carvalho de Melo wrote:
> 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);
>
Yes, will use zfree() here.
>> + }
>> +
>> + 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
>
Yes. If just allocation for one element, I should use zalloc().
Thanks
Jin Yao
>> + 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
>>
>
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