Re: [PATCH 3/8] perf record: Add BPF event filter support

From: Adrian Hunter
Date: Tue Mar 07 2023 - 08:07:28 EST

On 23/02/23 01:01, Namhyung Kim wrote:
> Use --filter option to set BPF filter for generic events other than the
> tracepoints or Intel PT. The BPF program will check the sample data and
> filter according to the expression.
>
> For example, the below is the typical perf record for frequency mode.
> The sample period started from 1 and increased gradually.
>
> $ sudo ./perf record -e cycles true
> $ sudo ./perf script
> perf-exec 2272336 546683.916875: 1 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916892: 1 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916899: 3 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916905: 17 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916911: 100 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916917: 589 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916924: 3470 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> perf-exec 2272336 546683.916930: 20465 cycles: ffffffff828499b8 perf_event_exec+0x298 ([kernel.kallsyms])
> true 2272336 546683.916940: 119873 cycles: ffffffff8283afdd perf_iterate_ctx+0x2d ([kernel.kallsyms])
> true 2272336 546683.917003: 461349 cycles: ffffffff82892517 vma_interval_tree_insert+0x37 ([kernel.kallsyms])
> true 2272336 546683.917237: 635778 cycles: ffffffff82a11400 security_mmap_file+0x20 ([kernel.kallsyms])
>
> When you add a BPF filter to get samples having periods greater than 1000,
> the output would look like below:
>
> $ sudo ./perf record -e cycles --filter 'period > 1000' true
> $ sudo ./perf script
> perf-exec 2273949 546850.708501: 5029 cycles: ffffffff826f9e25 finish_wait+0x5 ([kernel.kallsyms])
> perf-exec 2273949 546850.708508: 32409 cycles: ffffffff826f9e25 finish_wait+0x5 ([kernel.kallsyms])
> perf-exec 2273949 546850.708526: 143369 cycles: ffffffff82b4cdbf xas_start+0x5f ([kernel.kallsyms])
> perf-exec 2273949 546850.708600: 372650 cycles: ffffffff8286b8f7 __pagevec_lru_add+0x117 ([kernel.kallsyms])
> perf-exec 2273949 546850.708791: 482953 cycles: ffffffff829190de __mod_memcg_lruvec_state+0x4e ([kernel.kallsyms])
> true 2273949 546850.709036: 501985 cycles: ffffffff828add7c tlb_gather_mmu+0x4c ([kernel.kallsyms])
> true 2273949 546850.709292: 503065 cycles: 7f2446d97c03 _dl_map_object_deps+0x973 (/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)
>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> tools/perf/Documentation/perf-record.txt | 15 +++++++++++---
> tools/perf/util/bpf_counter.c | 3 +--
> tools/perf/util/evlist.c | 25 +++++++++++++++++-------
> tools/perf/util/evsel.c | 2 ++
> tools/perf/util/parse-events.c | 8 +++-----
> 5 files changed, 36 insertions(+), 17 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index ff815c2f67e8..9f4e1337e6dc 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -119,9 +119,12 @@ OPTIONS
> "perf report" to view group events together.
>
> --filter=<filter>::
> - Event filter. This option should follow an event selector (-e) which
> - selects either tracepoint event(s) or a hardware trace PMU
> - (e.g. Intel PT or CoreSight).
> + Event filter. This option should follow an event selector (-e).
> + If the event is a tracepoint, the filter string will be parsed by
> + the kernel. If the event is a hardware trace PMU (e.g. Intel PT
> + or CoreSight), it'll be processed as an address filter. Otherwise
> + it means a general filter using BPF which can be applied for any
> + kind of events.

events -> event

>
> - tracepoint filters
>
> @@ -174,6 +177,12 @@ OPTIONS
> within a single mapping. MMAP events (or /proc/<pid>/maps) can be
> examined to determine if that is a possibility.
>
> + - bpf filters
> +
> + BPF filter can access the sample data and make a decision based on the

'BPF filter' -> 'A BPF filter'

> + data. Users need to set the appropriate sample type to use the BPF

'the appropriate' -> 'an appropriate'

Perhaps could expand on what "appropriate sample type" means here,
also, since the user does not actually specify sample_type directly.

What happens if the sample_type is not appropriate?

> + filter.
> +
> Multiple filters can be separated with space or comma.
>
> --exclude-perf::
> diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
> index eeee899fcf34..0414385794ee 100644
> --- a/tools/perf/util/bpf_counter.c
> +++ b/tools/perf/util/bpf_counter.c
> @@ -781,8 +781,7 @@ extern struct bpf_counter_ops bperf_cgrp_ops;
>
> static inline bool bpf_counter_skip(struct evsel *evsel)
> {
> - return list_empty(&evsel->bpf_counter_list) &&
> - evsel->follower_skel == NULL;
> + return evsel->bpf_counter_ops == NULL;
> }
>
> int bpf_counter__install_pe(struct evsel *evsel, int cpu_map_idx, int fd)
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 817df2504a1e..1ae047b24c89 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -31,6 +31,7 @@
> #include "util/evlist-hybrid.h"
> #include "util/pmu.h"
> #include "util/sample.h"
> +#include "util/bpf-filter.h"
> #include <signal.h>
> #include <unistd.h>
> #include <sched.h>
> @@ -1086,17 +1087,27 @@ int evlist__apply_filters(struct evlist *evlist, struct evsel **err_evsel)
> int err = 0;
>
> evlist__for_each_entry(evlist, evsel) {
> - if (evsel->filter == NULL)
> - continue;
> -
> /*
> * filters only work for tracepoint event, which doesn't have cpu limit.
> * So evlist and evsel should always be same.
> */
> - err = perf_evsel__apply_filter(&evsel->core, evsel->filter);
> - if (err) {
> - *err_evsel = evsel;
> - break;
> + if (evsel->filter) {

Extra space before 'if'

> + err = perf_evsel__apply_filter(&evsel->core, evsel->filter);
> + if (err) {
> + *err_evsel = evsel;
> + break;
> + }
> + }
> +
> + /*
> + * non-tracepoint events can have BPF filters.
> + */
> + if (!list_empty(&evsel->bpf_filters)) {
> + err = perf_bpf_filter__prepare(evsel);
> + if (err) {
> + *err_evsel = evsel;
> + break;
> + }
> }
> }
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 51e8ce6edddc..cae624fde026 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -50,6 +50,7 @@
> #include "off_cpu.h"
> #include "../perf-sys.h"
> #include "util/parse-branch-options.h"
> +#include "util/bpf-filter.h"
> #include <internal/xyarray.h>
> #include <internal/lib.h>
> #include <internal/threadmap.h>
> @@ -1494,6 +1495,7 @@ void evsel__exit(struct evsel *evsel)
> assert(list_empty(&evsel->core.node));
> assert(evsel->evlist == NULL);
> bpf_counter__destroy(evsel);
> + perf_bpf_filter__destroy(evsel);
> evsel__free_counts(evsel);
> perf_evsel__free_fd(&evsel->core);
> perf_evsel__free_id(&evsel->core);
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 0336ff27c15f..4371a2bb2564 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -27,6 +27,7 @@
> #include "perf.h"
> #include "util/parse-events-hybrid.h"
> #include "util/pmu-hybrid.h"
> +#include "util/bpf-filter.h"
> #include "tracepoint.h"
> #include "thread_map.h"
>
> @@ -2537,11 +2538,8 @@ static int set_filter(struct evsel *evsel, const void *arg)
> perf_pmu__scan_file(pmu, "nr_addr_filters",
> "%d", &nr_addr_filters);
>
> - if (!nr_addr_filters) {
> - fprintf(stderr,
> - "This CPU does not support address filtering\n");
> - return -1;
> - }
> + if (!nr_addr_filters)
> + return perf_bpf_filter__parse(&evsel->bpf_filters, str);
>
> if (evsel__append_addr_filter(evsel, str) < 0) {
> fprintf(stderr,