Messages in this thread | | | From | Namhyung Kim <> | Date | Wed, 25 Oct 2023 12:04:16 -0700 | Subject | Re: [PATCH v3 20/50] perf record: Be lazier in allocating lost samples buffer |
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On Wed, Oct 25, 2023 at 10:01 AM Ian Rogers <irogers@google.com> wrote: > > On Tue, Oct 24, 2023 at 8:44 PM Yang Jihong <yangjihong1@huawei.com> wrote: > > > > Hello, > > > > On 2023/10/25 6:23, Ian Rogers wrote: > > > Wait until a lost sample occurs to allocate the lost samples buffer, > > > often the buffer isn't necessary. This saves a 64kb allocation and > > > 5.3kb of peak memory consumption. > > > > > > Signed-off-by: Ian Rogers <irogers@google.com> > > > --- > > > tools/perf/builtin-record.c | 29 +++++++++++++++++++---------- > > > 1 file changed, 19 insertions(+), 10 deletions(-) > > > > > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > > > index 9b4f3805ca92..b6c8c1371b39 100644 > > > --- a/tools/perf/builtin-record.c > > > +++ b/tools/perf/builtin-record.c > > > @@ -1924,21 +1924,13 @@ static void __record__save_lost_samples(struct record *rec, struct evsel *evsel, > > > static void record__read_lost_samples(struct record *rec) > > > { > > > struct perf_session *session = rec->session; > > > - struct perf_record_lost_samples *lost; > > > + struct perf_record_lost_samples *lost = NULL; > > > struct evsel *evsel; > > > > > > /* there was an error during record__open */ > > > if (session->evlist == NULL) > > > return; > > > > > > - lost = zalloc(PERF_SAMPLE_MAX_SIZE); > > > - if (lost == NULL) { > > > - pr_debug("Memory allocation failed\n"); > > > - return; > > > - } > > > - > > > - lost->header.type = PERF_RECORD_LOST_SAMPLES; > > > - > > > evlist__for_each_entry(session->evlist, evsel) { > > > struct xyarray *xy = evsel->core.sample_id; > > > u64 lost_count; > > > @@ -1961,6 +1953,14 @@ static void record__read_lost_samples(struct record *rec) > > > } > > > > > > if (count.lost) { > > > + if (!lost) { > > > + lost = zalloc(PERF_SAMPLE_MAX_SIZE); > > > + if (!lost) { > > > + pr_debug("Memory allocation failed\n"); > > > + return; > > > + } > > > + lost->header.type = PERF_RECORD_LOST_SAMPLES; > > > + } > > > __record__save_lost_samples(rec, evsel, lost, > > > x, y, count.lost, 0); > > > } > > > @@ -1968,9 +1968,18 @@ static void record__read_lost_samples(struct record *rec) > > > } > > > > > > lost_count = perf_bpf_filter__lost_count(evsel); > > > - if (lost_count) > > > + if (lost_count) { > > > + if (!lost) { > > > + lost = zalloc(PERF_SAMPLE_MAX_SIZE); > > > + if (!lost) { > > > + pr_debug("Memory allocation failed\n"); > > > + return; > > > + } > > > + lost->header.type = PERF_RECORD_LOST_SAMPLES; > > > + } > > > __record__save_lost_samples(rec, evsel, lost, 0, 0, lost_count, > > > PERF_RECORD_MISC_LOST_SAMPLES_BPF); > > > + } > > > } > > > > Can zalloc for `lost` be moved to __record__save_lost_samples? > > This simplifies the code. > > Hmm.. seems marginal. This change makes the code not return in > record__read_lost_samples when the memory allocation fails, so I'm > 50/50 on it.
Maybe you can make it return the failure.
> > > > > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > > index dcf288a4fb9a..8d2eb746031a 100644 > > --- a/tools/perf/builtin-record.c > > +++ b/tools/perf/builtin-record.c [SNIP] > > out: > > - free(lost); > > + if (lost) > > + free(lost);
This is unnecessary as free() can handle NULL pointers.
Thanks, Namhyung
> > } > > > > static volatile sig_atomic_t workload_exec_errno; > > > > > > Thanks, > > Yang > >
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