Merge tag 'perf-core-for-mingo' of... (dd2281be) · Commits · e / devices / android_kernel_teracube_2e

tools/build/Makefile.build

+2 −0

Original line number	Diff line number	Diff line
		@@ -57,6 +57,8 @@ quiet_cmd_cc_i_c = CPP $@
		quiet_cmd_cc_s_c = AS $@
		cmd_cc_s_c = $(CC) $(c_flags) -S -o $@ $<

		quiet_cmd_gen = GEN $@

		# Link agregate command
		# If there's nothing to link, create empty $@ object.
		quiet_cmd_ld_multi = LD $@

tools/build/feature/Makefile

+6 −1

Original line number	Diff line number	Diff line
		@@ -70,8 +70,13 @@ test-libelf.bin:
		test-glibc.bin:
		$(BUILD)

		DWARFLIBS := -ldw
		ifeq ($(findstring -static,${LDFLAGS}),-static)
		DWARFLIBS += -lelf -lebl -lz -llzma -lbz2
		endif

		test-dwarf.bin:
		$(BUILD) -ldw
		$(BUILD) $(DWARFLIBS)

		test-libelf-mmap.bin:
		$(BUILD) -lelf

tools/perf/.gitignore

+1 −0

Original line number	Diff line number	Diff line
		@@ -29,3 +29,4 @@ config.mak.autogen
		*.pyc
		*.pyo
		.config-detected
		util/intel-pt-decoder/inat-tables.c

tools/perf/Documentation/intel-pt.txt

0 → 100644

+588 −0

Original line number	Diff line number	Diff line
		Intel Processor Trace
		=====================

		Overview
		========

		Intel Processor Trace (Intel PT) is an extension of Intel Architecture that
		collects information about software execution such as control flow, execution
		modes and timings and formats it into highly compressed binary packets.
		Technical details are documented in the Intel 64 and IA-32 Architectures
		Software Developer Manuals, Chapter 36 Intel Processor Trace.

		Intel PT is first supported in Intel Core M and 5th generation Intel Core
		processors that are based on the Intel micro-architecture code name Broadwell.

		Trace data is collected by 'perf record' and stored within the perf.data file.
		See below for options to 'perf record'.

		Trace data must be 'decoded' which involves walking the object code and matching
		the trace data packets. For example a TNT packet only tells whether a
		conditional branch was taken or not taken, so to make use of that packet the
		decoder must know precisely which instruction was being executed.

		Decoding is done on-the-fly. The decoder outputs samples in the same format as
		samples output by perf hardware events, for example as though the "instructions"
		or "branches" events had been recorded. Presently 3 tools support this:
		'perf script', 'perf report' and 'perf inject'. See below for more information
		on using those tools.

		The main distinguishing feature of Intel PT is that the decoder can determine
		the exact flow of software execution. Intel PT can be used to understand why
		and how did software get to a certain point, or behave a certain way. The
		software does not have to be recompiled, so Intel PT works with debug or release
		builds, however the executed images are needed - which makes use in JIT-compiled
		environments, or with self-modified code, a challenge. Also symbols need to be
		provided to make sense of addresses.

		A limitation of Intel PT is that it produces huge amounts of trace data
		(hundreds of megabytes per second per core) which takes a long time to decode,
		for example two or three orders of magnitude longer than it took to collect.
		Another limitation is the performance impact of tracing, something that will
		vary depending on the use-case and architecture.


		Quickstart
		==========

		It is important to start small. That is because it is easy to capture vastly
		more data than can possibly be processed.

		The simplest thing to do with Intel PT is userspace profiling of small programs.
		Data is captured with 'perf record' e.g. to trace 'ls' userspace-only:

		perf record -e intel_pt//u ls

		And profiled with 'perf report' e.g.

		perf report

		To also trace kernel space presents a problem, namely kernel self-modifying
		code. A fairly good kernel image is available in /proc/kcore but to get an
		accurate image a copy of /proc/kcore needs to be made under the same conditions
		as the data capture. A script perf-with-kcore can do that, but beware that the
		script makes use of 'sudo' to copy /proc/kcore. If you have perf installed
		locally from the source tree you can do:

		~/libexec/perf-core/perf-with-kcore record pt_ls -e intel_pt// -- ls

		which will create a directory named 'pt_ls' and put the perf.data file and
		copies of /proc/kcore, /proc/kallsyms and /proc/modules into it. Then to use
		'perf report' becomes:

		~/libexec/perf-core/perf-with-kcore report pt_ls

		Because samples are synthesized after-the-fact, the sampling period can be
		selected for reporting. e.g. sample every microsecond

		~/libexec/perf-core/perf-with-kcore report pt_ls --itrace=i1usge

		See the sections below for more information about the --itrace option.

		Beware the smaller the period, the more samples that are produced, and the
		longer it takes to process them.

		Also note that the coarseness of Intel PT timing information will start to
		distort the statistical value of the sampling as the sampling period becomes
		smaller.

		To represent software control flow, "branches" samples are produced. By default
		a branch sample is synthesized for every single branch. To get an idea what
		data is available you can use the 'perf script' tool with no parameters, which
		will list all the samples.

		perf record -e intel_pt//u ls
		perf script

		An interesting field that is not printed by default is 'flags' which can be
		displayed as follows:

		perf script -Fcomm,tid,pid,time,cpu,event,trace,ip,sym,dso,addr,symoff,flags

		The flags are "bcrosyiABEx" which stand for branch, call, return, conditional,
		system, asynchronous, interrupt, transaction abort, trace begin, trace end, and
		in transaction, respectively.

		While it is possible to create scripts to analyze the data, an alternative
		approach is available to export the data to a postgresql database. Refer to
		script export-to-postgresql.py for more details, and to script
		call-graph-from-postgresql.py for an example of using the database.

		As mentioned above, it is easy to capture too much data. One way to limit the
		data captured is to use 'snapshot' mode which is explained further below.
		Refer to 'new snapshot option' and 'Intel PT modes of operation' further below.

		Another problem that will be experienced is decoder errors. They can be caused
		by inability to access the executed image, self-modified or JIT-ed code, or the
		inability to match side-band information (such as context switches and mmaps)
		which results in the decoder not knowing what code was executed.

		There is also the problem of perf not being able to copy the data fast enough,
		resulting in data lost because the buffer was full. See 'Buffer handling' below
		for more details.


		perf record
		===========

		new event
		---------

		The Intel PT kernel driver creates a new PMU for Intel PT. PMU events are
		selected by providing the PMU name followed by the "config" separated by slashes.
		An enhancement has been made to allow default "config" e.g. the option

		-e intel_pt//

		will use a default config value. Currently that is the same as

		-e intel_pt/tsc,noretcomp=0/

		which is the same as

		-e intel_pt/tsc=1,noretcomp=0/

		The config terms are listed in /sys/devices/intel_pt/format. They are bit
		fields within the config member of the struct perf_event_attr which is
		passed to the kernel by the perf_event_open system call. They correspond to bit
		fields in the IA32_RTIT_CTL MSR. Here is a list of them and their definitions:

		$ for f in `ls /sys/devices/intel_pt/format`;do
		> echo $f
		> cat /sys/devices/intel_pt/format/$f
		> done
		noretcomp
		config:11
		tsc
		config:10

		Note that the default config must be overridden for each term i.e.

		-e intel_pt/noretcomp=0/

		is the same as:

		-e intel_pt/tsc=1,noretcomp=0/

		So, to disable TSC packets use:

		-e intel_pt/tsc=0/

		It is also possible to specify the config value explicitly:

		-e intel_pt/config=0x400/

		Note that, as with all events, the event is suffixed with event modifiers:

		u userspace
		k kernel
		h hypervisor
		G guest
		H host
		p precise ip

		'h', 'G' and 'H' are for virtualization which is not supported by Intel PT.
		'p' is also not relevant to Intel PT. So only options 'u' and 'k' are
		meaningful for Intel PT.

		perf_event_attr is displayed if the -vv option is used e.g.

		------------------------------------------------------------
		perf_event_attr:
		type 6
		size 112
		config 0x400
		{ sample_period, sample_freq } 1
		sample_type IP\|TID\|TIME\|CPU\|IDENTIFIER
		read_format ID
		disabled 1
		inherit 1
		exclude_kernel 1
		exclude_hv 1
		enable_on_exec 1
		sample_id_all 1
		------------------------------------------------------------
		sys_perf_event_open: pid 31104 cpu 0 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 1 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 2 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 3 group_fd -1 flags 0x8
		------------------------------------------------------------


		new snapshot option
		-------------------

		To select snapshot mode a new option has been added:

		-S

		Optionally it can be followed by the snapshot size e.g.

		-S0x100000

		The default snapshot size is the auxtrace mmap size. If neither auxtrace mmap size
		nor snapshot size is specified, then the default is 4MiB for privileged users
		(or if /proc/sys/kernel/perf_event_paranoid < 0), 128KiB for unprivileged users.
		If an unprivileged user does not specify mmap pages, the mmap pages will be
		reduced as described in the 'new auxtrace mmap size option' section below.

		The snapshot size is displayed if the option -vv is used e.g.

		Intel PT snapshot size: %zu


		new auxtrace mmap size option
		---------------------------

		Intel PT buffer size is specified by an addition to the -m option e.g.

		-m,16

		selects a buffer size of 16 pages i.e. 64KiB.

		Note that the existing functionality of -m is unchanged. The auxtrace mmap size
		is specified by the optional addition of a comma and the value.

		The default auxtrace mmap size for Intel PT is 4MiB/page_size for privileged users
		(or if /proc/sys/kernel/perf_event_paranoid < 0), 128KiB for unprivileged users.
		If an unprivileged user does not specify mmap pages, the mmap pages will be
		reduced from the default 512KiB/page_size to 256KiB/page_size, otherwise the
		user is likely to get an error as they exceed their mlock limit (Max locked
		memory as shown in /proc/self/limits). Note that perf does not count the first
		512KiB (actually /proc/sys/kernel/perf_event_mlock_kb minus 1 page) per cpu
		against the mlock limit so an unprivileged user is allowed 512KiB per cpu plus
		their mlock limit (which defaults to 64KiB but is not multiplied by the number
		of cpus).

		In full-trace mode, powers of two are allowed for buffer size, with a minimum
		size of 2 pages. In snapshot mode, it is the same but the minimum size is
		1 page.

		The mmap size and auxtrace mmap size are displayed if the -vv option is used e.g.

		mmap length 528384
		auxtrace mmap length 4198400


		Intel PT modes of operation
		---------------------------

		Intel PT can be used in 2 modes:
		full-trace mode
		snapshot mode

		Full-trace mode traces continuously e.g.

		perf record -e intel_pt//u uname

		Snapshot mode captures the available data when a signal is sent e.g.

		perf record -v -e intel_pt//u -S ./loopy 1000000000 &
		[1] 11435
		kill -USR2 11435
		Recording AUX area tracing snapshot

		Note that the signal sent is SIGUSR2.
		Note that "Recording AUX area tracing snapshot" is displayed because the -v
		option is used.

		The 2 modes cannot be used together.


		Buffer handling
		---------------

		There may be buffer limitations (i.e. single ToPa entry) which means that actual
		buffer sizes are limited to powers of 2 up to 4MiB (MAX_ORDER). In order to
		provide other sizes, and in particular an arbitrarily large size, multiple
		buffers are logically concatenated. However an interrupt must be used to switch
		between buffers. That has two potential problems:
		a) the interrupt may not be handled in time so that the current buffer
		becomes full and some trace data is lost.
		b) the interrupts may slow the system and affect the performance
		results.

		If trace data is lost, the driver sets 'truncated' in the PERF_RECORD_AUX event
		which the tools report as an error.

		In full-trace mode, the driver waits for data to be copied out before allowing
		the (logical) buffer to wrap-around. If data is not copied out quickly enough,
		again 'truncated' is set in the PERF_RECORD_AUX event. If the driver has to
		wait, the intel_pt event gets disabled. Because it is difficult to know when
		that happens, perf tools always re-enable the intel_pt event after copying out
		data.


		Intel PT and build ids
		----------------------

		By default "perf record" post-processes the event stream to find all build ids
		for executables for all addresses sampled. Deliberately, Intel PT is not
		decoded for that purpose (it would take too long). Instead the build ids for
		all executables encountered (due to mmap, comm or task events) are included
		in the perf.data file.

		To see buildids included in the perf.data file use the command:

		perf buildid-list

		If the perf.data file contains Intel PT data, that is the same as:

		perf buildid-list --with-hits


		Snapshot mode and event disabling
		---------------------------------

		In order to make a snapshot, the intel_pt event is disabled using an IOCTL,
		namely PERF_EVENT_IOC_DISABLE. However doing that can also disable the
		collection of side-band information. In order to prevent that, a dummy
		software event has been introduced that permits tracking events (like mmaps) to
		continue to be recorded while intel_pt is disabled. That is important to ensure
		there is complete side-band information to allow the decoding of subsequent
		snapshots.

		A test has been created for that. To find the test:

		perf test list
		...
		23: Test using a dummy software event to keep tracking

		To run the test:

		perf test 23
		23: Test using a dummy software event to keep tracking : Ok


		perf record modes (nothing new here)
		------------------------------------

		perf record essentially operates in one of three modes:
		per thread
		per cpu
		workload only

		"per thread" mode is selected by -t or by --per-thread (with -p or -u or just a
		workload).
		"per cpu" is selected by -C or -a.
		"workload only" mode is selected by not using the other options but providing a
		command to run (i.e. the workload).

		In per-thread mode an exact list of threads is traced. There is no inheritance.
		Each thread has its own event buffer.

		In per-cpu mode all processes (or processes from the selected cgroup i.e. -G
		option, or processes selected with -p or -u) are traced. Each cpu has its own
		buffer. Inheritance is allowed.

		In workload-only mode, the workload is traced but with per-cpu buffers.
		Inheritance is allowed. Note that you can now trace a workload in per-thread
		mode by using the --per-thread option.


		Privileged vs non-privileged users
		----------------------------------

		Unless /proc/sys/kernel/perf_event_paranoid is set to -1, unprivileged users
		have memory limits imposed upon them. That affects what buffer sizes they can
		have as outlined above.

		Unless /proc/sys/kernel/perf_event_paranoid is set to -1, unprivileged users are
		not permitted to use tracepoints which means there is insufficient side-band
		information to decode Intel PT in per-cpu mode, and potentially workload-only
		mode too if the workload creates new processes.

		Note also, that to use tracepoints, read-access to debugfs is required. So if
		debugfs is not mounted or the user does not have read-access, it will again not
		be possible to decode Intel PT in per-cpu mode.


		sched_switch tracepoint
		-----------------------

		The sched_switch tracepoint is used to provide side-band data for Intel PT
		decoding. sched_switch events are automatically added. e.g. the second event
		shown below

		$ perf record -vv -e intel_pt//u uname
		------------------------------------------------------------
		perf_event_attr:
		type 6
		size 112
		config 0x400
		{ sample_period, sample_freq } 1
		sample_type IP\|TID\|TIME\|CPU\|IDENTIFIER
		read_format ID
		disabled 1
		inherit 1
		exclude_kernel 1
		exclude_hv 1
		enable_on_exec 1
		sample_id_all 1
		------------------------------------------------------------
		sys_perf_event_open: pid 31104 cpu 0 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 1 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 2 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 3 group_fd -1 flags 0x8
		------------------------------------------------------------
		perf_event_attr:
		type 2
		size 112
		config 0x108
		{ sample_period, sample_freq } 1
		sample_type IP\|TID\|TIME\|CPU\|PERIOD\|RAW\|IDENTIFIER
		read_format ID
		inherit 1
		sample_id_all 1
		exclude_guest 1
		------------------------------------------------------------
		sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8
		sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8
		sys_perf_event_open: pid -1 cpu 2 group_fd -1 flags 0x8
		sys_perf_event_open: pid -1 cpu 3 group_fd -1 flags 0x8
		------------------------------------------------------------
		perf_event_attr:
		type 1
		size 112
		config 0x9
		{ sample_period, sample_freq } 1
		sample_type IP\|TID\|TIME\|IDENTIFIER
		read_format ID
		disabled 1
		inherit 1
		exclude_kernel 1
		exclude_hv 1
		mmap 1
		comm 1
		enable_on_exec 1
		task 1
		sample_id_all 1
		mmap2 1
		comm_exec 1
		------------------------------------------------------------
		sys_perf_event_open: pid 31104 cpu 0 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 1 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 2 group_fd -1 flags 0x8
		sys_perf_event_open: pid 31104 cpu 3 group_fd -1 flags 0x8
		mmap size 528384B
		AUX area mmap length 4194304
		perf event ring buffer mmapped per cpu
		Synthesizing auxtrace information
		Linux
		[ perf record: Woken up 1 times to write data ]
		[ perf record: Captured and wrote 0.042 MB perf.data ]

		Note, the sched_switch event is only added if the user is permitted to use it
		and only in per-cpu mode.

		Note also, the sched_switch event is only added if TSC packets are requested.
		That is because, in the absence of timing information, the sched_switch events
		cannot be matched against the Intel PT trace.


		perf script
		===========

		By default, perf script will decode trace data found in the perf.data file.
		This can be further controlled by new option --itrace.


		New --itrace option
		-------------------

		Having no option is the same as

		--itrace

		which, in turn, is the same as

		--itrace=ibxe

		The letters are:

		i synthesize "instructions" events
		b synthesize "branches" events
		x synthesize "transactions" events
		c synthesize branches events (calls only)
		r synthesize branches events (returns only)
		e synthesize tracing error events
		d create a debug log
		g synthesize a call chain (use with i or x)

		"Instructions" events look like they were recorded by "perf record -e
		instructions".

		"Branches" events look like they were recorded by "perf record -e branches". "c"
		and "r" can be combined to get calls and returns.

		"Transactions" events correspond to the start or end of transactions. The
		'flags' field can be used in perf script to determine whether the event is a
		tranasaction start, commit or abort.

		Error events are new. They show where the decoder lost the trace. Error events
		are quite important. Users must know if what they are seeing is a complete
		picture or not.

		The "d" option will cause the creation of a file "intel_pt.log" containing all
		decoded packets and instructions. Note that this option slows down the decoder
		and that the resulting file may be very large.

		In addition, the period of the "instructions" event can be specified. e.g.

		--itrace=i10us

		sets the period to 10us i.e. one instruction sample is synthesized for each 10
		microseconds of trace. Alternatives to "us" are "ms" (milliseconds),
		"ns" (nanoseconds), "t" (TSC ticks) or "i" (instructions).

		"ms", "us" and "ns" are converted to TSC ticks.

		The timing information included with Intel PT does not give the time of every
		instruction. Consequently, for the purpose of sampling, the decoder estimates
		the time since the last timing packet based on 1 tick per instruction. The time
		on the sample is not adjusted and reflects the last known value of TSC.

		For Intel PT, the default period is 100us.

		Also the call chain size (default 16, max. 1024) for instructions or
		transactions events can be specified. e.g.

		--itrace=ig32
		--itrace=xg32

		To disable trace decoding entirely, use the option --no-itrace.


		dump option
		-----------

		perf script has an option (-D) to "dump" the events i.e. display the binary
		data.

		When -D is used, Intel PT packets are displayed. The packet decoder does not
		pay attention to PSB packets, but just decodes the bytes - so the packets seen
		by the actual decoder may not be identical in places where the data is corrupt.
		One example of that would be when the buffer-switching interrupt has been too
		slow, and the buffer has been filled completely. In that case, the last packet
		in the buffer might be truncated and immediately followed by a PSB as the trace
		continues in the next buffer.

		To disable the display of Intel PT packets, combine the -D option with
		--no-itrace.


		perf report
		===========

		By default, perf report will decode trace data found in the perf.data file.
		This can be further controlled by new option --itrace exactly the same as
		perf script, with the exception that the default is --itrace=igxe.


		perf inject
		===========

		perf inject also accepts the --itrace option in which case tracing data is
		removed and replaced with the synthesized events. e.g.

		perf inject --itrace -i perf.data -o perf.data.new

tools/perf/Makefile.perf

+10 −2

Original line number	Diff line number	Diff line
		@@ -76,6 +76,12 @@ include config/utilities.mak
		#
		# Define NO_AUXTRACE if you do not want AUX area tracing support

		# As per kernel Makefile, avoid funny character set dependencies
		unexport LC_ALL
		LC_COLLATE=C
		LC_NUMERIC=C
		export LC_COLLATE LC_NUMERIC

		ifeq ($(srctree),)
		srctree := $(patsubst %/,%,$(dir $(shell pwd)))
		srctree := $(patsubst %/,%,$(dir $(srctree)))
		@@ -135,6 +141,7 @@ INSTALL = install
		FLEX = flex
		BISON = bison
		STRIP = strip
		AWK = awk

		LIB_DIR = $(srctree)/tools/lib/api/
		TRACE_EVENT_DIR = $(srctree)/tools/lib/traceevent/
		@@ -289,7 +296,7 @@ strip: $(PROGRAMS) $(OUTPUT)perf

		PERF_IN := $(OUTPUT)perf-in.o

		export srctree OUTPUT RM CC LD AR CFLAGS V BISON FLEX
		export srctree OUTPUT RM CC LD AR CFLAGS V BISON FLEX AWK
		build := -f $(srctree)/tools/build/Makefile.build dir=. obj

		$(PERF_IN): $(OUTPUT)PERF-VERSION-FILE $(OUTPUT)common-cmds.h FORCE
		@@ -565,7 +572,8 @@ clean: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean config-clean
		$(Q)find . -name '.o' -delete -o -name '\..cmd' -delete -o -name '\.*.d' -delete
		$(Q)$(RM) $(OUTPUT).config-detected
		$(call QUIET_CLEAN, core-progs) $(RM) $(ALL_PROGRAMS) perf perf-read-vdso32 perf-read-vdsox32
		$(call QUIET_CLEAN, core-gen) $(RM) .spec .pyc .pyo /.pyc /.pyo $(OUTPUT)common-cmds.h TAGS tags cscope $(OUTPUT)PERF-VERSION-FILE $(OUTPUT)FEATURE-DUMP $(OUTPUT)util/-bison $(OUTPUT)util/-flex
		$(call QUIET_CLEAN, core-gen) $(RM) .spec .pyc .pyo /.pyc /.pyo $(OUTPUT)common-cmds.h TAGS tags cscope $(OUTPUT)PERF-VERSION-FILE $(OUTPUT)FEATURE-DUMP $(OUTPUT)util/-bison $(OUTPUT)util/-flex \
		$(OUTPUT)util/intel-pt-decoder/inat-tables.c
		$(QUIET_SUBDIR0)Documentation $(QUIET_SUBDIR1) clean
		$(python-clean)