From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: "Jiri Olsa" <jolsa@kernel.org>,
"Namhyung Kim" <namhyung@kernel.org>,
"Clark Williams" <williams@redhat.com>,
linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
"Arnaldo Carvalho de Melo" <acme@redhat.com>,
"Adrian Hunter" <adrian.hunter@intel.com>,
"Alexei Starovoitov" <ast@fb.com>,
"Andrii Nakryiko" <andrii.nakryiko@gmail.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Luis Cláudio Gonçalves" <lclaudio@redhat.com>,
"Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>,
"Wang Nan" <wangnan0@huawei.com>, "Yonghong Song" <yhs@fb.com>
Subject: [PATCH 17/35] perf bpf: Automatically add BTF ELF markers
Date: Thu, 7 Mar 2019 14:44:15 -0300 [thread overview]
Message-ID: <20190307174433.28819-18-acme@kernel.org> (raw)
In-Reply-To: <20190307174433.28819-1-acme@kernel.org>
From: Arnaldo Carvalho de Melo <acme@redhat.com>
The libbpf loader expects that some __btf_map_<MAP_NAME> structs be in
place with the keys and values types of maps so that one can store the
struct definitions and have them sent to the kernel via sys_bpf(fd, cmd
= BTF_LOAD) and then later be retrievable via sys_bpf(fd, cmd =
BPF_OBJ_GET_INFO_BY_FD) for use by tools such as 'bpftool map dump id
MAP_ID'.
Since we already have this for defining maps in 'perf trace' BPF events:
bpf_map(name, _type, type_key, type_val, _max_entries)
As used in the tools/perf/examples/bpf/augmented_raw_syscalls.c:
--- 8< ---
struct syscall {
bool enabled;
};
bpf_map(syscalls, ARRAY, int, struct syscall, 512);
--- 8< ---
All we need is to get all that already available info, piggyback on the
'bpf_map' define in tools/perf/include/bpf/bpf.h, that is included by
'perf trace' BPF programs and do that without requiring changes to the
BPF programs already defining maps using 'bpf_map()'.
So this is what we have before this patch:
1) With this in ~/.perfconfig to dump .c events as .o, aka save a copy
so that we can use the .o later as a pre-compiled BPF bytecode:
# grep '\[llvm\]' -A2 ~/.perfconfig
[llvm]
dump-obj = true
clang-opt = -g
#
# clang --version
clang version 9.0.0 (https://git.llvm.org/git/clang.git/ 7906282d3afec5dfdc2b27943fd6c0309086c507) (https://git.llvm.org/git/llvm.git/ a1b5de1ff8ae8bc79dc8e86e1f82565229bd0500)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/llvm/bin
2) Note the -g there so that we get clang to generate debuginfo, and
since the target is 'bpf' it will generate the BTF info in this
clang version (9.0).
3) Run a simple 'perf record' specifiying as an event the augmented_raw_syscalls.c
source code:
# perf record -e /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.c sleep 1
LLVM: dumping /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.025 MB perf.data ]
# file /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
/home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o: ELF 64-bit LSB relocatable, eBPF, version 1 (SYSV), with debug_info, not stripped
4) Look at the BTF structs encoded in it:
# pahole -F btf --sizes /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
syscall_enter_args 64 0
augmented_filename 264 0
syscall 1 0
syscall_exit_args 24 0
bpf_map 28 0
#
# pahole -F btf -C syscalls /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
# pahole -F btf -C syscall /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
struct syscall {
bool enabled; /* 0 1 */
/* size: 1, cachelines: 1, members: 1 */
/* last cacheline: 1 bytes */
};
#
5) Ok, with just this we don't have the markers expected by the libbpf
loader and when we run with this BPF bytecode, because we have:
# grep '\[trace\]' -A1 ~/.perfconfig
[trace]
add_events = /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
#
6) Lets do a 'perf trace' system wide session using this BPF program:
# perf trace -e *mmsg,open*
Cache2 I/O/6885 openat(AT_FDCWD, "/home/acme/.cache/mozilla/firefox/ina67tev.default/cache2/entries/BA220AB2914006A7AE96D27BE6EA13DD77519FCA", O_RDWR|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR) = 106
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
Cache2 I/O/6885 openat(AT_FDCWD, "/proc/self/mountinfo", O_RDONLY) = 121
DNS Res~ver #3/23340 openat(AT_FDCWD, "/etc/hosts", O_RDONLY|O_CLOEXEC) = 106
DNS Res~ver #3/23340 sendmmsg(106<socket:[3482690]>, 0x7f252f1fcaf0, 2, MSG_NOSIGNAL) = 2
Cache2 I/O/6885 openat(AT_FDCWD, "/home/acme/.cache/mozilla/firefox/ina67tev.default/cache2/entries/BA220AB2914006A7AE96D27BE6EA13DD77519FCA", O_RDWR) = 106
lighttpd/18915 openat(AT_FDCWD, "/proc/loadavg", O_RDONLY) = 12
7) While it runs lets see the maps that 'perf trace' + libbpf's BPF
loader loaded into the kernel via sys_bpf(fd, BPF_BTF_LOAD, ...):
# bpftool map list | tail -6
149: perf_event_array name __augmented_sys flags 0x0
key 4B value 4B max_entries 8 memlock 4096B
150: array name syscalls flags 0x0
key 4B value 1B max_entries 512 memlock 8192B
151: hash name pids_filtered flags 0x0
key 4B value 1B max_entries 64 memlock 8192B
#
8) Dump the "pids_filtered", map, that will have one entry per PID that
'perf trace' wants filtered, which includes its own, to avoid a
tracing feedback loop (perf trace shows the syscalls it does which
generates more syscalls that it has to show that...), it also
auto-filters the 'gnome-terminal' and 'sshd' parent PIDs, for the
same reason:
# bpftool map dump id 151
key: a5 0c 00 00 value: 01
key: 14 63 00 00 value: 01
Found 2 elements
#
9) Since there is no BTF info available, it does a generic hex dump :-\
10) Now, with this patch applied, we'll do steps 3 to 6 again and look
with pahole if there are extra structs encoded in BTF:
# pahole -F btf --sizes /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
syscall_enter_args 64 0
augmented_filename 264 0
syscall 1 0
syscall_exit_args 24 0
bpf_map 28 0
____btf_map___augmented_syscalls__ 8 0
____btf_map_syscalls 8 0
____btf_map_pids_filtered 8 0
#
11) Yes, those __btf_map_ + the map names, lets see how they look like:
# pahole -F btf -C ____btf_map_syscalls /home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
struct ____btf_map_syscalls {
int key; /* 0 4 */
struct syscall value; /* 4 1 */
/* size: 8, cachelines: 1, members: 2 */
/* padding: 3 */
/* last cacheline: 8 bytes */
};
#
12) Lets repeat step 7 to get the new map ids:
# bpftool map list | tail -6
155: perf_event_array name __augmented_sys flags 0x0
key 4B value 4B max_entries 8 memlock 4096B
156: array name syscalls flags 0x0
key 4B value 1B max_entries 512 memlock 8192B
157: hash name pids_filtered flags 0x0
key 4B value 1B max_entries 64 memlock 8192B
#
13) And finally lets dump the 'pids_filtered':
# bpftool map dump id 157
[{
"key": 3237,
"value": true
},{
"key": 26435,
"value": true
}
]
#
Looks much better! BTF info was used to interpret the key as an integer
and the value as a struct with just one boolean member, so to make it
more compact, show just the 'true' value where we saw '01'.
Now to make 'perf trace --dump-map' to use BTF!
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-ybuf9wpkm30xk28iq7jbwb40@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/include/bpf/bpf.h | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/tools/perf/include/bpf/bpf.h b/tools/perf/include/bpf/bpf.h
index 5df7ed9d9020..2eac6d804b2d 100644
--- a/tools/perf/include/bpf/bpf.h
+++ b/tools/perf/include/bpf/bpf.h
@@ -24,7 +24,13 @@ struct bpf_map SEC("maps") name = { \
.key_size = sizeof(type_key), \
.value_size = sizeof(type_val), \
.max_entries = _max_entries, \
-}
+}; \
+struct ____btf_map_##name { \
+ type_key key; \
+ type_val value; \
+}; \
+struct ____btf_map_##name __attribute__((section(".maps." #name), used)) \
+ ____btf_map_##name = { }
/*
* FIXME: this should receive .max_entries as a parameter, as careful
--
2.20.1
next prev parent reply other threads:[~2019-03-07 17:44 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 17:43 [GIT PULL 00/35] perf/core improvements and fixes Arnaldo Carvalho de Melo
2019-03-07 17:43 ` [PATCH 01/35] perf, bpf: Consider events with attr.bpf_event as side-band events Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 02/35] perf probe: Clarify error message about not finding kernel modules debuginfo Arnaldo Carvalho de Melo
2019-03-07 23:30 ` Masami Hiramatsu
2019-03-07 23:58 ` Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 03/35] tools lib traceevent: Fix buffer overflow in arg_eval Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 04/35] perf: Mark expected switch fall-through Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 05/35] perf time-utils: Refactor time range parsing code Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 06/35] perf auxtrace: Improve address filter error message when there is no DSO Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 07/35] perf intel-pt: Fix divide by zero when TSC is not available Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 08/35] perf db-export: Add calls parent_id to enable creation of call trees Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 09/35] perf scripts python: export-to-sqlite.py: Export calls parent_id Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 10/35] perf scripts python: export-to-postgresql.py: Fix invalid input syntax for integer error Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 11/35] perf scripts python: export-to-postgresql.py: Export calls parent_id Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 12/35] perf scripts python: exported-sql-viewer.py: Factor out TreeWindowBase Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 13/35] perf scripts python: exported-sql-viewer.py: Improve TreeModel abstraction Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 14/35] perf scripts python: exported-sql-viewer.py: Factor out CallGraphModelBase Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 15/35] perf scripts python: exported-sql-viewer.py: Add call tree Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 16/35] perf beauty msg_flags: Add missing %s lost when adding prefix suppression logic Arnaldo Carvalho de Melo
2019-03-07 17:44 ` Arnaldo Carvalho de Melo [this message]
2019-03-07 17:44 ` [PATCH 18/35] perf clang: Remove needless extra semicolon Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 19/35] perf annotate: Calculate the max instruction name, align column to that Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 20/35] perf thread: Generalize function to copy from thread addr space from intel-bts code Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 21/35] perf diff: Support --time filter option Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 22/35] perf diff: Support --cpu " Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 23/35] perf diff: Support --pid/--tid filter options Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 24/35] perf script python: Remove mixed indentation Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 25/35] perf script python: Add Python3 support to futex-contention.py Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 26/35] perf script python: add Python3 support to check-perf-trace.py Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 27/35] perf script python: Add Python3 support to event_analyzing_sample.py Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 28/35] perf script python: Add Python3 support to intel-pt-events.py Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 29/35] perf c2c: Fix c2c report for empty numa node Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 30/35] perf hist: Add error path into hist_entry__init Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 31/35] perf hist: Fix memory leak of srcline Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 32/35] perf tools: Read and store caps/max_precise in perf_pmu Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 33/35] perf evsel: Probe for precise_ip with simple attr Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 34/35] perf session: Fix double free in perf_data__close Arnaldo Carvalho de Melo
2019-03-07 17:44 ` [PATCH 35/35] perf data: Force perf_data__open|close zero data->file.path Arnaldo Carvalho de Melo
2019-03-09 16:02 ` [GIT PULL 00/35] perf/core improvements and fixes Ingo Molnar
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