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Date: Fri, 28 Feb 2020 10:14:50 -0300
From: Arnaldo Carvalho de Melo <acme@...hat.com>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
bpf@...r.kernel.org, Andrii Nakryiko <andriin@...com>,
Yonghong Song <yhs@...com>, Song Liu <songliubraving@...com>,
Martin KaFai Lau <kafai@...com>,
Jakub Kicinski <kuba@...nel.org>,
David Miller <davem@...hat.com>,
Björn Töpel <bjorn.topel@...el.com>,
John Fastabend <john.fastabend@...il.com>,
Jesper Dangaard Brouer <hawk@...nel.org>
Subject: Re: [PATCH 16/18] perf tools: Synthesize bpf_trampoline/dispatcher
ksymbol event
Em Wed, Feb 26, 2020 at 02:03:43PM +0100, Jiri Olsa escreveu:
> Synthesize bpf images (trampolines/dispatchers) on start,
> as ksymbol events from /proc/kallsyms. Having this perf
> can recognize samples from those images and perf report
> and top shows them correctly.
>
> The rest of the ksymbol handling is already in place from
> for the bpf programs monitoring, so only the initial state
> was needed.
Acked-by: Arnaldo Carvalho de Melo <acme@...hat.com>
But at some point we should try and consolidate all those
kallsym__parse() calls we have in tools/perf/ not to do it that many
times, see below _before_ this patch:
[root@...e ~]# perf probe -x ~/bin/perf kallsyms__parse
Added new event:
probe_perf:kallsyms__parse (on kallsyms__parse in /home/acme/bin/perf)
You can now use it in all perf tools, such as:
perf record -e probe_perf:kallsyms__parse -aR sleep 1
[root@...e ~]# perf trace -e probe_perf:kallsyms__parse/max-stack=8/ -- perf record sleep 1
0.000 perf/6444 probe_perf:kallsyms__parse(__probe_ip: 4904384)
kallsyms__parse (/home/acme/bin/perf)
machine__get_running_kernel_start (/home/acme/bin/perf)
machine__create_kernel_maps (/home/acme/bin/perf)
perf_session__new (/home/acme/bin/perf)
cmd_record (/home/acme/bin/perf)
run_builtin (/home/acme/bin/perf)
main (/home/acme/bin/perf)
__libc_start_main (/usr/lib64/libc-2.30.so)
0.124 perf/6444 probe_perf:kallsyms__parse(__probe_ip: 4904384)
kallsyms__parse (/home/acme/bin/perf)
machine__get_running_kernel_start (/home/acme/bin/perf)
machine__create_kernel_maps (/home/acme/bin/perf)
perf_session__new (/home/acme/bin/perf)
cmd_record (/home/acme/bin/perf)
run_builtin (/home/acme/bin/perf)
main (/home/acme/bin/perf)
__libc_start_main (/usr/lib64/libc-2.30.so)
15.489 perf/6444 probe_perf:kallsyms__parse(__probe_ip: 4904384)
kallsyms__parse (/home/acme/bin/perf)
machine__create_kernel_maps (/home/acme/bin/perf)
perf_session__new (/home/acme/bin/perf)
cmd_record (/home/acme/bin/perf)
run_builtin (/home/acme/bin/perf)
main (/home/acme/bin/perf)
__libc_start_main (/usr/lib64/libc-2.30.so)
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data (7 samples) ]
[root@...e ~]#
- Arnaldo
> perf report output:
>
> # Overhead Command Shared Object Symbol
>
> 12.37% test_progs [kernel.vmlinux] [k] entry_SYSCALL_64
> 11.80% test_progs [kernel.vmlinux] [k] syscall_return_via_sysret
> 9.63% test_progs bpf_prog_bcf7977d3b93787c_prog2 [k] bpf_prog_bcf7977d3b93787c_prog2
> 6.90% test_progs bpf_trampoline_24456 [k] bpf_trampoline_24456
> 6.36% test_progs [kernel.vmlinux] [k] memcpy_erms
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
> tools/perf/util/bpf-event.c | 98 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 98 insertions(+)
>
> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> index a3207d900339..120ec547ae75 100644
> --- a/tools/perf/util/bpf-event.c
> +++ b/tools/perf/util/bpf-event.c
> @@ -6,6 +6,9 @@
> #include <bpf/libbpf.h>
> #include <linux/btf.h>
> #include <linux/err.h>
> +#include <linux/string.h>
> +#include <internal/lib.h>
> +#include <symbol/kallsyms.h>
> #include "bpf-event.h"
> #include "debug.h"
> #include "dso.h"
> @@ -290,11 +293,87 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
> return err ? -1 : 0;
> }
>
> +struct kallsyms_parse {
> + union perf_event *event;
> + perf_event__handler_t process;
> + struct machine *machine;
> + struct perf_tool *tool;
> +};
> +
> +static int
> +process_bpf_image(char *name, u64 addr, struct kallsyms_parse *data)
> +{
> + struct machine *machine = data->machine;
> + union perf_event *event = data->event;
> + struct perf_record_ksymbol *ksymbol;
> + u32 size;
> +
> + ksymbol = &event->ksymbol;
> +
> + /*
> + * The bpf image (trampoline/dispatcher) size is aligned to
> + * page, while it starts little bit after the page boundary.
> + */
> + size = page_size - (addr - PERF_ALIGN(addr, page_size));
> +
> + *ksymbol = (struct perf_record_ksymbol) {
> + .header = {
> + .type = PERF_RECORD_KSYMBOL,
> + .size = offsetof(struct perf_record_ksymbol, name),
> + },
> + .addr = addr,
> + .len = size,
> + .ksym_type = PERF_RECORD_KSYMBOL_TYPE_BPF,
> + .flags = 0,
> + };
> +
> + strncpy(ksymbol->name, name, KSYM_NAME_LEN);
> + ksymbol->header.size += PERF_ALIGN(strlen(name) + 1, sizeof(u64));
> + memset((void *) event + event->header.size, 0, machine->id_hdr_size);
> + event->header.size += machine->id_hdr_size;
> +
> + return perf_tool__process_synth_event(data->tool, event, machine,
> + data->process);
> +}
> +
> +static int
> +kallsyms_process_symbol(void *data, const char *_name,
> + char type __maybe_unused, u64 start)
> +{
> + char *module, *name;
> + unsigned long id;
> + int err = 0;
> +
> + module = strchr(_name, '\t');
> + if (!module)
> + return 0;
> +
> + /* We are going after [bpf] module ... */
> + if (strcmp(module + 1, "[bpf]"))
> + return 0;
> +
> + name = memdup(_name, (module - _name) + 1);
> + if (!name)
> + return -ENOMEM;
> +
> + name[module - _name] = 0;
> +
> + /* .. and only for trampolines and dispatchers */
> + if ((sscanf(name, "bpf_trampoline_%lu", &id) == 1) ||
> + (sscanf(name, "bpf_dispatcher_%lu", &id) == 1))
> + err = process_bpf_image(name, start, data);
> +
> + free(name);
> + return err;
> +}
> +
> int perf_event__synthesize_bpf_events(struct perf_session *session,
> perf_event__handler_t process,
> struct machine *machine,
> struct record_opts *opts)
> {
> + const char *kallsyms_filename = "/proc/kallsyms";
> + struct kallsyms_parse arg;
> union perf_event *event;
> __u32 id = 0;
> int err;
> @@ -303,6 +382,8 @@ int perf_event__synthesize_bpf_events(struct perf_session *session,
> event = malloc(sizeof(event->bpf) + KSYM_NAME_LEN + machine->id_hdr_size);
> if (!event)
> return -1;
> +
> + /* Synthesize all the bpf programs in system. */
> while (true) {
> err = bpf_prog_get_next_id(id, &id);
> if (err) {
> @@ -335,6 +416,23 @@ int perf_event__synthesize_bpf_events(struct perf_session *session,
> break;
> }
> }
> +
> + /* Synthesize all the bpf images - trampolines/dispatchers. */
> + if (symbol_conf.kallsyms_name != NULL)
> + kallsyms_filename = symbol_conf.kallsyms_name;
> +
> + arg = (struct kallsyms_parse) {
> + .event = event,
> + .process = process,
> + .machine = machine,
> + .tool = session->tool,
> + };
> +
> + if (kallsyms__parse(kallsyms_filename, &arg, kallsyms_process_symbol)) {
> + pr_err("%s: failed to synthesize bpf images: %s\n",
> + __func__, strerror(errno));
> + }
> +
> free(event);
> return err;
> }
> --
> 2.24.1
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