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Date: Tue, 28 Feb 2023 16:03:27 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Leo Yan <leo.yan@...aro.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
James Clark <james.clark@....com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 09/14] perf kvm: Use histograms list to replace cached list
On Tue, Feb 28, 2023 at 3:53 AM Leo Yan <leo.yan@...aro.org> wrote:
>
> perf kvm tool defines its own cached list which is managed with RB tree,
> histograms also provide RB tree to manage data entries. Since now we
> have introduced histograms in the tool, it's not necessary to use the
> self defined list and we can directly use histograms list to manage
> KVM events.
>
> This patch changes to use histograms list to track KVM events, and it
> invokes the common function hists__output_resort_cb() to sort result,
> this also give us flexibility to extend more sorting key words easily.
>
> After histograms list supported, the cached list is redundant so remove
> the relevant code for it.
>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> Reviewed-by: James Clark <james.clark@....com>
> ---
> tools/perf/builtin-kvm.c | 186 +++++++++++++++++++------------------
> tools/perf/util/kvm-stat.h | 7 --
> 2 files changed, 94 insertions(+), 99 deletions(-)
>
> diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
> index da84f5063d4d..32dc697ff707 100644
> --- a/tools/perf/builtin-kvm.c
> +++ b/tools/perf/builtin-kvm.c
> @@ -421,44 +421,37 @@ struct vcpu_event_record {
> struct kvm_event *last_event;
> };
>
> -
> -static void init_kvm_event_record(struct perf_kvm_stat *kvm)
> -{
> - unsigned int i;
> -
> - for (i = 0; i < EVENTS_CACHE_SIZE; i++)
> - INIT_LIST_HEAD(&kvm->kvm_events_cache[i]);
> -}
> -
> #ifdef HAVE_TIMERFD_SUPPORT
> -static void clear_events_cache_stats(struct list_head *kvm_events_cache)
> +static void clear_events_cache_stats(void)
> {
> - struct list_head *head;
> + struct rb_root_cached *root;
> + struct rb_node *nd;
> struct kvm_event *event;
> - unsigned int i;
> - int j;
> -
> - for (i = 0; i < EVENTS_CACHE_SIZE; i++) {
> - head = &kvm_events_cache[i];
> - list_for_each_entry(event, head, hash_entry) {
> - /* reset stats for event */
> - event->total.time = 0;
> - init_stats(&event->total.stats);
> -
> - for (j = 0; j < event->max_vcpu; ++j) {
> - event->vcpu[j].time = 0;
> - init_stats(&event->vcpu[j].stats);
> - }
> + int i;
> +
> + if (hists__has(&kvm_hists.hists, need_collapse))
> + root = &kvm_hists.hists.entries_collapsed;
> + else
> + root = kvm_hists.hists.entries_in;
> +
> + for (nd = rb_first_cached(root); nd; nd = rb_next(nd)) {
> + struct hist_entry *he;
> +
> + he = rb_entry(nd, struct hist_entry, rb_node_in);
> + event = container_of(he, struct kvm_event, he);
> +
> + /* reset stats for event */
> + event->total.time = 0;
> + init_stats(&event->total.stats);
> +
> + for (i = 0; i < event->max_vcpu; ++i) {
> + event->vcpu[i].time = 0;
> + init_stats(&event->vcpu[i].stats);
> }
> }
> }
> #endif
>
> -static int kvm_events_hash_fn(u64 key)
> -{
> - return key & (EVENTS_CACHE_SIZE - 1);
> -}
> -
> static bool kvm_event_expand(struct kvm_event *event, int vcpu_id)
> {
> int old_max_vcpu = event->max_vcpu;
> @@ -484,21 +477,51 @@ static bool kvm_event_expand(struct kvm_event *event, int vcpu_id)
> return true;
> }
>
> +static void *kvm_he_zalloc(size_t size)
> +{
> + struct kvm_event *kvm_ev;
> +
> + kvm_ev = zalloc(size + sizeof(*kvm_ev));
> + if (!kvm_ev)
> + return NULL;
> +
> + return &kvm_ev->he;
> +}
> +
> +static void kvm_he_free(void *he)
> +{
> + struct kvm_event *kvm_ev;
> +
> + kvm_ev = container_of(he, struct kvm_event, he);
> + free(kvm_ev);
> +}
> +
> +static struct hist_entry_ops kvm_ev_entry_ops = {
> + .new = kvm_he_zalloc,
> + .free = kvm_he_free,
> +};
> +
> static struct kvm_event *kvm_alloc_init_event(struct perf_kvm_stat *kvm,
> struct event_key *key,
> - struct perf_sample *sample __maybe_unused)
> + struct perf_sample *sample)
> {
> struct kvm_event *event;
> + struct hist_entry *he;
>
> - event = zalloc(sizeof(*event));
> - if (!event) {
> - pr_err("Not enough memory\n");
> + he = hists__add_entry_ops(&kvm_hists.hists, &kvm_ev_entry_ops,
> + &kvm->al, NULL, NULL, NULL, sample, true);
> + if (he == NULL) {
> + pr_err("Failed to allocate hist entry\n");
> return NULL;
> }
>
> + hists__inc_nr_samples(&kvm_hists.hists, 0);
> +
> + event = container_of(he, struct kvm_event, he);
> event->perf_kvm = kvm;
> event->key = *key;
> init_stats(&event->total.stats);
> +
> return event;
> }
>
> @@ -507,22 +530,26 @@ static struct kvm_event *find_create_kvm_event(struct perf_kvm_stat *kvm,
> struct perf_sample *sample)
> {
> struct kvm_event *event;
> - struct list_head *head;
> + struct rb_root_cached *root;
> + struct rb_node *nd;
>
> BUG_ON(key->key == INVALID_KEY);
>
> - head = &kvm->kvm_events_cache[kvm_events_hash_fn(key->key)];
> - list_for_each_entry(event, head, hash_entry) {
> + if (hists__has(&kvm_hists.hists, need_collapse))
> + root = &kvm_hists.hists.entries_collapsed;
> + else
> + root = kvm_hists.hists.entries_in;
> +
> + for (nd = rb_first_cached(root); nd; nd = rb_next(nd)) {
> + struct hist_entry *he = rb_entry(nd, struct hist_entry,
> + rb_node_in);
> +
> + event = container_of(he, struct kvm_event, he);
> if (event->key.key == key->key && event->key.info == key->info)
> return event;
This seems inefficient and even unnecessary. You should find
the event based on the return value of hist_entry__cmp() from
the root and go down.
But I think that's what hists__add_entry_ops() does. Maybe
you may need to move the init logic (like init_stats) to the
kvm_he_zalloc().
Thanks,
Namhyung
> }
>
> - event = kvm_alloc_init_event(kvm, key, sample);
> - if (!event)
> - return NULL;
> -
> - list_add(&event->hash_entry, head);
> - return event;
> + return kvm_alloc_init_event(kvm, key, sample);
> }
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