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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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470530bbb8
Implement a --mmap-flush option that specifies minimal number of bytes
that is extracted from mmaped kernel buffer to store into a trace. The
default option value is 1 byte what means every time trace writing
thread finds some new data in the mmaped buffer the data is extracted,
possibly compressed and written to a trace.
$ tools/perf/perf record --mmap-flush 1024 -e cycles -- matrix.gcc
$ tools/perf/perf record --aio --mmap-flush 1K -e cycles -- matrix.gcc
The option is independent from -z setting, doesn't vary with compression
level and can serve two purposes.
The first purpose is to increase the compression ratio of a trace data.
Larger data chunks are compressed more effectively so the implemented
option allows specifying data chunk size to compress. Also at some cases
executing more write syscalls with smaller data size can take longer
than executing less write syscalls with bigger data size due to syscall
overhead so extracting bigger data chunks specified by the option value
could additionally decrease runtime overhead.
The second purpose is to avoid self monitoring live-lock issue in system
wide (-a) profiling mode. Profiling in system wide mode with compression
(-a -z) can additionally induce data into the kernel buffers along with
the data from monitored processes. If performance data rate and volume
from the monitored processes is high then trace streaming and
compression activity in the tool is also high. High tool process
activity can lead to subtle live-lock effect when compression of single
new byte from some of mmaped kernel buffer leads to generation of the
next single byte at some mmaped buffer. So perf tool process ends up in
endless self monitoring.
Implemented synch parameter is the mean to force data move independently
from the specified flush threshold value. Despite the provided flush
value the tool needs capability to unconditionally drain memory buffers,
at least in the end of the collection.
Committer testing:
Running with the default value, i.e. as soon as there is something to
read go on consuming, we first write the synthesized events, small
chunks of about 128 bytes:
# perf trace -m 2048 --call-graph dwarf -e write -- perf record
<SNIP>
101.142 ( 0.004 ms): perf/25821 write(fd: 3</root/perf.data>, buf: 0x210db60, count: 120) = 120
__libc_write (/usr/lib64/libpthread-2.28.so)
ion (/home/acme/bin/perf)
record__write (inlined)
process_synthesized_event (/home/acme/bin/perf)
perf_tool__process_synth_event (inlined)
perf_event__synthesize_mmap_events (/home/acme/bin/perf)
Then we move to reading the mmap buffers consuming the events put there
by the kernel perf infrastructure:
107.561 ( 0.005 ms): perf/25821 write(fd: 3</root/perf.data>, buf: 0x7f1befc02000, count: 336) = 336
__libc_write (/usr/lib64/libpthread-2.28.so)
ion (/home/acme/bin/perf)
record__write (inlined)
record__pushfn (/home/acme/bin/perf)
perf_mmap__push (/home/acme/bin/perf)
record__mmap_read_evlist (inlined)
record__mmap_read_all (inlined)
__cmd_record (inlined)
cmd_record (/home/acme/bin/perf)
12919.953 ( 0.136 ms): perf/25821 write(fd: 3</root/perf.data>, buf: 0x7f1befc83150, count: 184984) = 184984
<SNIP same backtrace as in the 107.561 timestamp>
12920.094 ( 0.155 ms): perf/25821 write(fd: 3</root/perf.data>, buf: 0x7f1befc02150, count: 261816) = 261816
<SNIP same backtrace as in the 107.561 timestamp>
12920.253 ( 0.093 ms): perf/25821 write(fd: 3</root/perf.data>, buf: 0x7f1befb81120, count: 170832) = 170832
<SNIP same backtrace as in the 107.561 timestamp>
If we limit it to write only when more than 16MB are available for
reading, it throttles that to a quarter of the --mmap-pages set for
'perf record', which by default get to 528384 bytes, found out using
'record -v':
mmap flush: 132096
mmap size 528384B
With that in place all the writes coming from
record__mmap_read_evlist(), i.e. from the mmap buffers setup by the
kernel perf infrastructure were at least 132096 bytes long.
Trying with a bigger mmap size:
perf trace -e write perf record -v -m 2048 --mmap-flush 16M
74982.928 ( 2.471 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff94a6cc000, count: 3580888) = 3580888
74985.406 ( 2.353 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff949ecb000, count: 3453256) = 3453256
74987.764 ( 2.629 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff9496ca000, count: 3859232) = 3859232
74990.399 ( 2.341 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff948ec9000, count: 3769032) = 3769032
74992.744 ( 2.064 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff9486c8000, count: 3310520) = 3310520
74994.814 ( 2.619 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff947ec7000, count: 4194688) = 4194688
74997.439 ( 2.787 ms): perf/26500 write(fd: 3</root/perf.data>, buf: 0x7ff9476c6000, count: 4029760) = 4029760
Was again limited to a quarter of the mmap size:
mmap flush: 2098176
mmap size 8392704B
A warning about that would be good to have but can be added later,
something like:
"max flush is a quarter of the mmap size, if wanting to bump the mmap
flush further, bump the mmap size as well using -m/--mmap-pages"
Also rename the 'sync' parameters to 'synch' to keep tools/perf building
with older glibcs:
cc1: warnings being treated as errors
builtin-record.c: In function 'record__mmap_read_evlist':
builtin-record.c:775: warning: declaration of 'sync' shadows a global declaration
/usr/include/unistd.h:933: warning: shadowed declaration is here
builtin-record.c: In function 'record__mmap_read_all':
builtin-record.c:856: warning: declaration of 'sync' shadows a global declaration
/usr/include/unistd.h:933: warning: shadowed declaration is here
Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/f6600d72-ecfa-2eb7-7e51-f6954547d500@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
105 lines
2.4 KiB
C
105 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _PERF_PERF_H
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#define _PERF_PERF_H
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#include <time.h>
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#include <stdbool.h>
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#include <linux/types.h>
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#include <linux/stddef.h>
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#include <linux/perf_event.h>
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extern bool test_attr__enabled;
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void test_attr__ready(void);
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void test_attr__init(void);
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void test_attr__open(struct perf_event_attr *attr, pid_t pid, int cpu,
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int fd, int group_fd, unsigned long flags);
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#define HAVE_ATTR_TEST
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#include "perf-sys.h"
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static inline unsigned long long rdclock(void)
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{
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struct timespec ts;
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clock_gettime(CLOCK_MONOTONIC, &ts);
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return ts.tv_sec * 1000000000ULL + ts.tv_nsec;
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}
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#ifndef MAX_NR_CPUS
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#define MAX_NR_CPUS 1024
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#endif
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extern const char *input_name;
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extern bool perf_host, perf_guest;
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extern const char perf_version_string[];
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void pthread__unblock_sigwinch(void);
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#include "util/target.h"
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struct record_opts {
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struct target target;
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bool group;
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bool inherit_stat;
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bool no_buffering;
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bool no_inherit;
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bool no_inherit_set;
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bool no_samples;
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bool raw_samples;
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bool sample_address;
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bool sample_phys_addr;
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bool sample_weight;
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bool sample_time;
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bool sample_time_set;
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bool sample_cpu;
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bool period;
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bool period_set;
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bool running_time;
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bool full_auxtrace;
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bool auxtrace_snapshot_mode;
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bool record_namespaces;
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bool record_switch_events;
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bool all_kernel;
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bool all_user;
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bool tail_synthesize;
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bool overwrite;
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bool ignore_missing_thread;
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bool strict_freq;
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bool sample_id;
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bool no_bpf_event;
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unsigned int freq;
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unsigned int mmap_pages;
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unsigned int auxtrace_mmap_pages;
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unsigned int user_freq;
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u64 branch_stack;
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u64 sample_intr_regs;
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u64 sample_user_regs;
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u64 default_interval;
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u64 user_interval;
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size_t auxtrace_snapshot_size;
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const char *auxtrace_snapshot_opts;
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bool sample_transaction;
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unsigned initial_delay;
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bool use_clockid;
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clockid_t clockid;
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u64 clockid_res_ns;
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int nr_cblocks;
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int affinity;
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int mmap_flush;
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};
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enum perf_affinity {
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PERF_AFFINITY_SYS = 0,
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PERF_AFFINITY_NODE,
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PERF_AFFINITY_CPU,
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PERF_AFFINITY_MAX
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};
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struct option;
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extern const char * const *record_usage;
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extern struct option *record_options;
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extern int version_verbose;
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int record__parse_freq(const struct option *opt, const char *str, int unset);
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#endif
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