perf tools maintainership:
- Add git information for perf-tools and perf-tools-next trees/branches to the
MAINTAINERS file. That is where development now takes place and myself and
Namhyung Kim have write access, more people to come as we emulate other
maintainer groups.
perf record:
- Record kernel data maps when 'perf record --data' is used, so that global variables can
be resolved and used in tools that do data profiling.
perf trace:
- Remove the old, experimental support for BPF events in which a .c file was passed as
an event: "perf trace -e hello.c" to then get compiled and loaded.
The only known usage for that, that shipped with the kernel as an example for such events,
augmented the raw_syscalls tracepoints and was converted to a libbpf skeleton, reusing all
the user space components and the BPF code connected to the syscalls.
In the end just the way to glue the BPF part and the user space type beautifiers changed,
now being performed by libbpf skeletons.
The next step is to use BTF to do pretty printing of all syscall types, as discussed with
Alan Maguire and others.
Now, on a perf built with BUILD_BPF_SKEL=1 we get most if not all path/filenames/strings,
some of the networking data structures, perf_event_attr, etc, i.e. systemwide tracing of
nanosleep calls and perf_event_open syscalls while 'perf stat' runs 'sleep' for 5 seconds:
# perf trace -a -e *nanosleep,perf* perf stat -e cycles,instructions sleep 5
0.000 ( 9.034 ms): perf/327641 perf_event_open(attr_uptr: { type: 0 (PERF_TYPE_HARDWARE), size: 136, config: 0 (PERF_COUNT_HW_CPU_CYCLES), sample_type: IDENTIFIER, read_format: TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING, disabled: 1, inherit: 1, enable_on_exec: 1, exclude_guest: 1 }, pid: 327642 (perf), cpu: -1, group_fd: -1, flags: FD_CLOEXEC) = 3
9.039 ( 0.006 ms): perf/327641 perf_event_open(attr_uptr: { type: 0 (PERF_TYPE_HARDWARE), size: 136, config: 0x1 (PERF_COUNT_HW_INSTRUCTIONS), sample_type: IDENTIFIER, read_format: TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING, disabled: 1, inherit: 1, enable_on_exec: 1, exclude_guest: 1 }, pid: 327642 (perf-exec), cpu: -1, group_fd: -1, flags: FD_CLOEXEC) = 4
? ( ): gpm/991 ... [continued]: clock_nanosleep()) = 0
10.133 ( ): sleep/327642 clock_nanosleep(rqtp: { .tv_sec: 5, .tv_nsec: 0 }, rmtp: 0x7ffd36f83ed0) ...
? ( ): pool-gsd-smart/3051 ... [continued]: clock_nanosleep()) = 0
30.276 ( ): gpm/991 clock_nanosleep(rqtp: { .tv_sec: 2, .tv_nsec: 0 }, rmtp: 0x7ffcc6f73710) ...
223.215 (1000.430 ms): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) = 0
30.276 (2000.394 ms): gpm/991 ... [continued]: clock_nanosleep()) = 0
1230.814 ( ): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) ...
1230.814 (1000.404 ms): pool-gsd-smart/3051 ... [continued]: clock_nanosleep()) = 0
2030.886 ( ): gpm/991 clock_nanosleep(rqtp: { .tv_sec: 2, .tv_nsec: 0 }, rmtp: 0x7ffcc6f73710) ...
2237.709 (1000.153 ms): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) = 0
? ( ): crond/1172 ... [continued]: clock_nanosleep()) = 0
3242.699 ( ): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) ...
2030.886 (2000.385 ms): gpm/991 ... [continued]: clock_nanosleep()) = 0
3728.078 ( ): crond/1172 clock_nanosleep(rqtp: { .tv_sec: 60, .tv_nsec: 0 }, rmtp: 0x7ffe0971dcf0) ...
3242.699 (1000.158 ms): pool-gsd-smart/3051 ... [continued]: clock_nanosleep()) = 0
4031.409 ( ): gpm/991 clock_nanosleep(rqtp: { .tv_sec: 2, .tv_nsec: 0 }, rmtp: 0x7ffcc6f73710) ...
10.133 (5000.375 ms): sleep/327642 ... [continued]: clock_nanosleep()) = 0
Performance counter stats for 'sleep 5':
2,617,347 cycles
1,855,997 instructions # 0.71 insn per cycle
5.002282128 seconds time elapsed
0.000855000 seconds user
0.000852000 seconds sys
#
perf annotate:
- Building with binutils' libopcode now is opt-in (BUILD_NONDISTRO=1) for
licensing reasons, and we missed a build test on tools/perf/tests makefile.
Since we now default to NDEBUG=1, we ended up segfaulting when building with
BUILD_NONDISTRO=1 because a needed initialization routine was being "error
checked" via an assert.
Fix it by explicitly checking the result and aborting instead if it fails.
We better back propagate the error, but at least 'perf annotate' on samples
collected for a BPF program is back working when perf is built with
BUILD_NONDISTRO=1.
perf report/top:
- Add back TUI hierarchy mode header, that is seen when using 'perf report/top --hierarchy'.
- Fix the number of entries for 'e' key in the TUI that was preventing navigation of
lines when expanding an entry.
perf report/script:
- Support cross platform register handling, allowing a perf.data file collected
on one architecture to have registers sampled correctly displayed when
analysis tools such as 'perf report' and 'perf script' are used on a different
architecture.
- Fix handling of event attributes in pipe mode, i.e. when one uses:
perf record -o - | perf report -i -
When no perf.data files are used.
- Handle files generated via pipe mode with a version of perf and then read
also via pipe mode with a different version of perf, where the event attr
record may have changed, use the record size field to properly support this
version mismatch.
perf probe:
- Accessing global variables from uprobes isn't supported, make the error
message state that instead of stating that some minimal kernel version is
needed to have that feature. This seems just a tool limitation, the kernel
probably has all that is needed.
perf tests:
- Fix a reference count related leak in the dlfilter v0 API where the result
of a thread__find_symbol_fb() is not matched with an addr_location__exit()
to drop the reference counts of the resolved components (machine, thread, map,
symbol, etc). Add a dlfilter test to make sure that doesn't regresses.
- Lots of fixes for the 'perf test' written in shell script related to problems
found with the shellcheck utility.
- Fixes for 'perf test' shell scripts testing features enabled when perf is
built with BUILD_BPF_SKEL=1, such as 'perf stat' bpf counters.
- Add perf record sample filtering test, things like the following example, that gets
implemented as a BPF filter attached to the event:
# perf record -e task-clock -c 10000 --filter 'ip < 0xffffffff00000000'
- Improve the way the task_analyzer test checks if libtraceevent is linked,
using 'perf version --build-options' instead of the more expensinve
'perf record -e "sched:sched_switch"'.
- Add support for riscv in the mmap-basic test. (This went as well via the RiscV tree, same contents).
libperf:
- Implement riscv mmap support (This went as well via the RiscV tree, same contents).
perf script:
- New tool that converts perf.data files to the firefox profiler format so that one can use
the visualizer at https://profiler.firefox.com/. Done by Anup Sharma as part of this year's
Google Summer of Code.
One can generate the output and upload it to the web interface but Anup also automated
everything:
perf script gecko -F 99 -a sleep 60
- Support syscall name parsing on arm64.
- Print "cgroup" field on the same line as "comm".
perf bench:
- Add new 'uprobe' benchmark to measure the overhead of uprobes with/without
BPF programs attached to it.
- breakpoints are not available on power9, skip that test.
perf stat:
- Add #num_cpus_online literal to be used in 'perf stat' metrics, and add this extra
'perf test' check that exemplifies its purpose:
TEST_ASSERT_VAL("#num_cpus_online",
expr__parse(&num_cpus_online, ctx, "#num_cpus_online") == 0);
TEST_ASSERT_VAL("#num_cpus", expr__parse(&num_cpus, ctx, "#num_cpus") == 0);
TEST_ASSERT_VAL("#num_cpus >= #num_cpus_online", num_cpus >= num_cpus_online);
Miscellaneous:
- Improve tool startup time by lazily reading PMU, JSON, sysfs data.
- Improve error reporting in the parsing of events, passing YYLTYPE to error routines,
so that the output can show were the parsing error was found.
- Add 'perf test' entries to check the parsing of events improvements.
- Fix various leak for things detected by -fsanitize=address, mostly things that would
be freed at tool exit, including:
- Free evsel->filter on the destructor.
- Allow tools to register a thread->priv destructor and use it in 'perf trace'.
- Free evsel->priv in 'perf trace'.
- Free string returned by synthesize_perf_probe_point() when the caller fails
to do all it needs.
- Adjust various compiler options to not consider errors some warnings when
building with broken headers found in things like python, flex, bison, as we
otherwise build with -Werror. Some for gcc, some for clang, some for some
specific version of those, some for some specific version of flex or bison, or
some specific combination of these components, bah.
- Allow customization of clang options for BPF target, this helps building on
gentoo where there are other oddities where BPF targets gets passed some compiler
options intended for the native build, so building with WERROR=0 helps while
these oddities are fixed.
- Dont pass ERR_PTR() values to perf_session__delete() in 'perf top' and 'perf lock',
fixing some segfaults when handling some odd failures.
- Add LTO build option.
- Fix format of unordered lists in the perf docs (tools/perf/Documentation).
- Overhaul the bison files, using constructs such as YYNOMEM.
- Remove unused tokens from the bison .y files.
- Add more comments to various structs.
- A few LoongArch enablement patches.
Vendor events (JSON):
- Add JSON metrics for Yitian 710 DDR (aarch64). Things like:
EventName, BriefDescription
visible_window_limit_reached_rd, "At least one entry in read queue reaches the visible window limit.",
visible_window_limit_reached_wr, "At least one entry in write queue reaches the visible window limit.",
op_is_dqsosc_mpc , "A DQS Oscillator MPC command to DRAM.",
op_is_dqsosc_mrr , "A DQS Oscillator MRR command to DRAM.",
op_is_tcr_mrr , "A Temperature Compensated Refresh(TCR) MRR command to DRAM.",
- Add AmpereOne metrics (aarch64).
- Update N2 and V2 metrics (aarch64) and events using Arm telemetry repo.
- Update scale units and descriptions of common topdown metrics on aarch64. Things like:
- "MetricExpr": "stall_slot_frontend / (#slots * cpu_cycles)",
- "BriefDescription": "Frontend bound L1 topdown metric",
+ "MetricExpr": "100 * (stall_slot_frontend / (#slots * cpu_cycles))",
+ "BriefDescription": "This metric is the percentage of total slots that were stalled due to resource constraints in the frontend of the processor.",
- Update events for intel: meteorlake to 1.04, sapphirerapids to 1.15, Icelake+ metric constraints.
- Update files for the power10 platform.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-----BEGIN PGP SIGNATURE-----
iHUEABYKAB0WIQR2GiIUctdOfX2qHhGyPKLppCJ+JwUCZPfJZgAKCRCyPKLppCJ+
J1/eAP9lgtavD0V75wy1p5zyotkceOmPTkk1DYFVx2Euhxa/lAD/YW/JvuVSo0Gr
HqJP52XaV0tF8gG+YxL+Lay/Ke0P5AQ=
=d12c
-----END PGP SIGNATURE-----
Merge tag 'perf-tools-for-v6.6-1-2023-09-05' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools
Pull perf tools updates from Arnaldo Carvalho de Melo:
"perf tools maintainership:
- Add git information for perf-tools and perf-tools-next trees and
branches to the MAINTAINERS file. That is where development now
takes place and myself and Namhyung Kim have write access, more
people to come as we emulate other maintainer groups.
perf record:
- Record kernel data maps when 'perf record --data' is used, so that
global variables can be resolved and used in tools that do data
profiling.
perf trace:
- Remove the old, experimental support for BPF events in which a .c
file was passed as an event: "perf trace -e hello.c" to then get
compiled and loaded.
The only known usage for that, that shipped with the kernel as an
example for such events, augmented the raw_syscalls tracepoints and
was converted to a libbpf skeleton, reusing all the user space
components and the BPF code connected to the syscalls.
In the end just the way to glue the BPF part and the user space
type beautifiers changed, now being performed by libbpf skeletons.
The next step is to use BTF to do pretty printing of all syscall
types, as discussed with Alan Maguire and others.
Now, on a perf built with BUILD_BPF_SKEL=1 we get most if not all
path/filenames/strings, some of the networking data structures,
perf_event_attr, etc, i.e. systemwide tracing of nanosleep calls
and perf_event_open syscalls while 'perf stat' runs 'sleep' for 5
seconds:
# perf trace -a -e *nanosleep,perf* perf stat -e cycles,instructions sleep 5
0.000 ( 9.034 ms): perf/327641 perf_event_open(attr_uptr: { type: 0 (PERF_TYPE_HARDWARE), size: 136, config: 0 (PERF_COUNT_HW_CPU_CYCLES), sample_type: IDENTIFIER, read_format: TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING, disabled: 1, inherit: 1, enable_on_exec: 1, exclude_guest: 1 }, pid: 327642 (perf), cpu: -1, group_fd: -1, flags: FD_CLOEXEC) = 3
9.039 ( 0.006 ms): perf/327641 perf_event_open(attr_uptr: { type: 0 (PERF_TYPE_HARDWARE), size: 136, config: 0x1 (PERF_COUNT_HW_INSTRUCTIONS), sample_type: IDENTIFIER, read_format: TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING, disabled: 1, inherit: 1, enable_on_exec: 1, exclude_guest: 1 }, pid: 327642 (perf-exec), cpu: -1, group_fd: -1, flags: FD_CLOEXEC) = 4
? ( ): gpm/991 ... [continued]: clock_nanosleep()) = 0
10.133 ( ): sleep/327642 clock_nanosleep(rqtp: { .tv_sec: 5, .tv_nsec: 0 }, rmtp: 0x7ffd36f83ed0) ...
? ( ): pool-gsd-smart/3051 ... [continued]: clock_nanosleep()) = 0
30.276 ( ): gpm/991 clock_nanosleep(rqtp: { .tv_sec: 2, .tv_nsec: 0 }, rmtp: 0x7ffcc6f73710) ...
223.215 (1000.430 ms): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) = 0
30.276 (2000.394 ms): gpm/991 ... [continued]: clock_nanosleep()) = 0
1230.814 ( ): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) ...
1230.814 (1000.404 ms): pool-gsd-smart/3051 ... [continued]: clock_nanosleep()) = 0
2030.886 ( ): gpm/991 clock_nanosleep(rqtp: { .tv_sec: 2, .tv_nsec: 0 }, rmtp: 0x7ffcc6f73710) ...
2237.709 (1000.153 ms): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) = 0
? ( ): crond/1172 ... [continued]: clock_nanosleep()) = 0
3242.699 ( ): pool-gsd-smart/3051 clock_nanosleep(rqtp: { .tv_sec: 1, .tv_nsec: 0 }, rmtp: 0x7f6e7fffec90) ...
2030.886 (2000.385 ms): gpm/991 ... [continued]: clock_nanosleep()) = 0
3728.078 ( ): crond/1172 clock_nanosleep(rqtp: { .tv_sec: 60, .tv_nsec: 0 }, rmtp: 0x7ffe0971dcf0) ...
3242.699 (1000.158 ms): pool-gsd-smart/3051 ... [continued]: clock_nanosleep()) = 0
4031.409 ( ): gpm/991 clock_nanosleep(rqtp: { .tv_sec: 2, .tv_nsec: 0 }, rmtp: 0x7ffcc6f73710) ...
10.133 (5000.375 ms): sleep/327642 ... [continued]: clock_nanosleep()) = 0
Performance counter stats for 'sleep 5':
2,617,347 cycles
1,855,997 instructions # 0.71 insn per cycle
5.002282128 seconds time elapsed
0.000855000 seconds user
0.000852000 seconds sys
perf annotate:
- Building with binutils' libopcode now is opt-in (BUILD_NONDISTRO=1)
for licensing reasons, and we missed a build test on
tools/perf/tests makefile.
Since we now default to NDEBUG=1, we ended up segfaulting when
building with BUILD_NONDISTRO=1 because a needed initialization
routine was being "error checked" via an assert.
Fix it by explicitly checking the result and aborting instead if it
fails.
We better back propagate the error, but at least 'perf annotate' on
samples collected for a BPF program is back working when perf is
built with BUILD_NONDISTRO=1.
perf report/top:
- Add back TUI hierarchy mode header, that is seen when using 'perf
report/top --hierarchy'.
- Fix the number of entries for 'e' key in the TUI that was
preventing navigation of lines when expanding an entry.
perf report/script:
- Support cross platform register handling, allowing a perf.data file
collected on one architecture to have registers sampled correctly
displayed when analysis tools such as 'perf report' and 'perf
script' are used on a different architecture.
- Fix handling of event attributes in pipe mode, i.e. when one uses:
perf record -o - | perf report -i -
When no perf.data files are used.
- Handle files generated via pipe mode with a version of perf and
then read also via pipe mode with a different version of perf,
where the event attr record may have changed, use the record size
field to properly support this version mismatch.
perf probe:
- Accessing global variables from uprobes isn't supported, make the
error message state that instead of stating that some minimal
kernel version is needed to have that feature. This seems just a
tool limitation, the kernel probably has all that is needed.
perf tests:
- Fix a reference count related leak in the dlfilter v0 API where the
result of a thread__find_symbol_fb() is not matched with an
addr_location__exit() to drop the reference counts of the resolved
components (machine, thread, map, symbol, etc). Add a dlfilter test
to make sure that doesn't regresses.
- Lots of fixes for the 'perf test' written in shell script related
to problems found with the shellcheck utility.
- Fixes for 'perf test' shell scripts testing features enabled when
perf is built with BUILD_BPF_SKEL=1, such as 'perf stat' bpf
counters.
- Add perf record sample filtering test, things like the following
example, that gets implemented as a BPF filter attached to the
event:
# perf record -e task-clock -c 10000 --filter 'ip < 0xffffffff00000000'
- Improve the way the task_analyzer test checks if libtraceevent is
linked, using 'perf version --build-options' instead of the more
expensinve 'perf record -e "sched:sched_switch"'.
- Add support for riscv in the mmap-basic test. (This went as well
via the RiscV tree, same contents).
libperf:
- Implement riscv mmap support (This went as well via the RiscV tree,
same contents).
perf script:
- New tool that converts perf.data files to the firefox profiler
format so that one can use the visualizer at
https://profiler.firefox.com/. Done by Anup Sharma as part of this
year's Google Summer of Code.
One can generate the output and upload it to the web interface but
Anup also automated everything:
perf script gecko -F 99 -a sleep 60
- Support syscall name parsing on arm64.
- Print "cgroup" field on the same line as "comm".
perf bench:
- Add new 'uprobe' benchmark to measure the overhead of uprobes
with/without BPF programs attached to it.
- breakpoints are not available on power9, skip that test.
perf stat:
- Add #num_cpus_online literal to be used in 'perf stat' metrics, and
add this extra 'perf test' check that exemplifies its purpose:
TEST_ASSERT_VAL("#num_cpus_online",
expr__parse(&num_cpus_online, ctx, "#num_cpus_online") == 0);
TEST_ASSERT_VAL("#num_cpus", expr__parse(&num_cpus, ctx, "#num_cpus") == 0);
TEST_ASSERT_VAL("#num_cpus >= #num_cpus_online", num_cpus >= num_cpus_online);
Miscellaneous:
- Improve tool startup time by lazily reading PMU, JSON, sysfs data.
- Improve error reporting in the parsing of events, passing YYLTYPE
to error routines, so that the output can show were the parsing
error was found.
- Add 'perf test' entries to check the parsing of events
improvements.
- Fix various leak for things detected by -fsanitize=address, mostly
things that would be freed at tool exit, including:
- Free evsel->filter on the destructor.
- Allow tools to register a thread->priv destructor and use it in
'perf trace'.
- Free evsel->priv in 'perf trace'.
- Free string returned by synthesize_perf_probe_point() when the
caller fails to do all it needs.
- Adjust various compiler options to not consider errors some
warnings when building with broken headers found in things like
python, flex, bison, as we otherwise build with -Werror. Some for
gcc, some for clang, some for some specific version of those, some
for some specific version of flex or bison, or some specific
combination of these components, bah.
- Allow customization of clang options for BPF target, this helps
building on gentoo where there are other oddities where BPF targets
gets passed some compiler options intended for the native build, so
building with WERROR=0 helps while these oddities are fixed.
- Dont pass ERR_PTR() values to perf_session__delete() in 'perf top'
and 'perf lock', fixing some segfaults when handling some odd
failures.
- Add LTO build option.
- Fix format of unordered lists in the perf docs
(tools/perf/Documentation)
- Overhaul the bison files, using constructs such as YYNOMEM.
- Remove unused tokens from the bison .y files.
- Add more comments to various structs.
- A few LoongArch enablement patches.
Vendor events (JSON):
- Add JSON metrics for Yitian 710 DDR (aarch64). Things like:
EventName, BriefDescription
visible_window_limit_reached_rd, "At least one entry in read queue reaches the visible window limit.",
visible_window_limit_reached_wr, "At least one entry in write queue reaches the visible window limit.",
op_is_dqsosc_mpc , "A DQS Oscillator MPC command to DRAM.",
op_is_dqsosc_mrr , "A DQS Oscillator MRR command to DRAM.",
op_is_tcr_mrr , "A Temperature Compensated Refresh(TCR) MRR command to DRAM.",
- Add AmpereOne metrics (aarch64).
- Update N2 and V2 metrics (aarch64) and events using Arm telemetry
repo.
- Update scale units and descriptions of common topdown metrics on
aarch64. Things like:
- "MetricExpr": "stall_slot_frontend / (#slots * cpu_cycles)",
- "BriefDescription": "Frontend bound L1 topdown metric",
+ "MetricExpr": "100 * (stall_slot_frontend / (#slots * cpu_cycles))",
+ "BriefDescription": "This metric is the percentage of total slots that were stalled due to resource constraints in the frontend of the processor.",
- Update events for intel: meteorlake to 1.04, sapphirerapids to
1.15, Icelake+ metric constraints.
- Update files for the power10 platform"
* tag 'perf-tools-for-v6.6-1-2023-09-05' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools: (217 commits)
perf parse-events: Fix driver config term
perf parse-events: Fixes relating to no_value terms
perf parse-events: Fix propagation of term's no_value when cloning
perf parse-events: Name the two term enums
perf list: Don't print Unit for "default_core"
perf vendor events intel: Fix modifier in tma_info_system_mem_parallel_reads for skylake
perf dlfilter: Avoid leak in v0 API test use of resolve_address()
perf metric: Add #num_cpus_online literal
perf pmu: Remove str from perf_pmu_alias
perf parse-events: Make common term list to strbuf helper
perf parse-events: Minor help message improvements
perf pmu: Avoid uninitialized use of alias->str
perf jevents: Use "default_core" for events with no Unit
perf test stat_bpf_counters_cgrp: Enhance perf stat cgroup BPF counter test
perf test shell stat_bpf_counters: Fix test on Intel
perf test shell record_bpf_filter: Skip 6.2 kernel
libperf: Get rid of attr.id field
perf tools: Convert to perf_record_header_attr_id()
libperf: Add perf_record_header_attr_id()
perf tools: Handle old data in PERF_RECORD_ATTR
...
.. _readme:
Linux kernel release 6.x <http://kernel.org/>
=============================================
These are the release notes for Linux version 6. Read them carefully,
as they tell you what this is all about, explain how to install the
kernel, and what to do if something goes wrong.
What is Linux?
--------------
Linux is a clone of the operating system Unix, written from scratch by
Linus Torvalds with assistance from a loosely-knit team of hackers across
the Net. It aims towards POSIX and Single UNIX Specification compliance.
It has all the features you would expect in a modern fully-fledged Unix,
including true multitasking, virtual memory, shared libraries, demand
loading, shared copy-on-write executables, proper memory management,
and multistack networking including IPv4 and IPv6.
It is distributed under the GNU General Public License v2 - see the
accompanying COPYING file for more details.
On what hardware does it run?
-----------------------------
Although originally developed first for 32-bit x86-based PCs (386 or higher),
today Linux also runs on (at least) the Compaq Alpha AXP, Sun SPARC and
UltraSPARC, Motorola 68000, PowerPC, PowerPC64, ARM, Hitachi SuperH, Cell,
IBM S/390, MIPS, HP PA-RISC, Intel IA-64, DEC VAX, AMD x86-64 Xtensa, and
ARC architectures.
Linux is easily portable to most general-purpose 32- or 64-bit architectures
as long as they have a paged memory management unit (PMMU) and a port of the
GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has
also been ported to a number of architectures without a PMMU, although
functionality is then obviously somewhat limited.
Linux has also been ported to itself. You can now run the kernel as a
userspace application - this is called UserMode Linux (UML).
Documentation
-------------
- There is a lot of documentation available both in electronic form on
the Internet and in books, both Linux-specific and pertaining to
general UNIX questions. I'd recommend looking into the documentation
subdirectories on any Linux FTP site for the LDP (Linux Documentation
Project) books. This README is not meant to be documentation on the
system: there are much better sources available.
- There are various README files in the Documentation/ subdirectory:
these typically contain kernel-specific installation notes for some
drivers for example. Please read the
:ref:`Documentation/process/changes.rst <changes>` file, as it
contains information about the problems, which may result by upgrading
your kernel.
Installing the kernel source
----------------------------
- If you install the full sources, put the kernel tarball in a
directory where you have permissions (e.g. your home directory) and
unpack it::
xz -cd linux-6.x.tar.xz | tar xvf -
Replace "X" with the version number of the latest kernel.
Do NOT use the /usr/src/linux area! This area has a (usually
incomplete) set of kernel headers that are used by the library header
files. They should match the library, and not get messed up by
whatever the kernel-du-jour happens to be.
- You can also upgrade between 6.x releases by patching. Patches are
distributed in the xz format. To install by patching, get all the
newer patch files, enter the top level directory of the kernel source
(linux-6.x) and execute::
xz -cd ../patch-6.x.xz | patch -p1
Replace "x" for all versions bigger than the version "x" of your current
source tree, **in_order**, and you should be ok. You may want to remove
the backup files (some-file-name~ or some-file-name.orig), and make sure
that there are no failed patches (some-file-name# or some-file-name.rej).
If there are, either you or I have made a mistake.
Unlike patches for the 6.x kernels, patches for the 6.x.y kernels
(also known as the -stable kernels) are not incremental but instead apply
directly to the base 6.x kernel. For example, if your base kernel is 6.0
and you want to apply the 6.0.3 patch, you must not first apply the 6.0.1
and 6.0.2 patches. Similarly, if you are running kernel version 6.0.2 and
want to jump to 6.0.3, you must first reverse the 6.0.2 patch (that is,
patch -R) **before** applying the 6.0.3 patch. You can read more on this in
:ref:`Documentation/process/applying-patches.rst <applying_patches>`.
Alternatively, the script patch-kernel can be used to automate this
process. It determines the current kernel version and applies any
patches found::
linux/scripts/patch-kernel linux
The first argument in the command above is the location of the
kernel source. Patches are applied from the current directory, but
an alternative directory can be specified as the second argument.
- Make sure you have no stale .o files and dependencies lying around::
cd linux
make mrproper
You should now have the sources correctly installed.
Software requirements
---------------------
Compiling and running the 6.x kernels requires up-to-date
versions of various software packages. Consult
:ref:`Documentation/process/changes.rst <changes>` for the minimum version numbers
required and how to get updates for these packages. Beware that using
excessively old versions of these packages can cause indirect
errors that are very difficult to track down, so don't assume that
you can just update packages when obvious problems arise during
build or operation.
Build directory for the kernel
------------------------------
When compiling the kernel, all output files will per default be
stored together with the kernel source code.
Using the option ``make O=output/dir`` allows you to specify an alternate
place for the output files (including .config).
Example::
kernel source code: /usr/src/linux-6.x
build directory: /home/name/build/kernel
To configure and build the kernel, use::
cd /usr/src/linux-6.x
make O=/home/name/build/kernel menuconfig
make O=/home/name/build/kernel
sudo make O=/home/name/build/kernel modules_install install
Please note: If the ``O=output/dir`` option is used, then it must be
used for all invocations of make.
Configuring the kernel
----------------------
Do not skip this step even if you are only upgrading one minor
version. New configuration options are added in each release, and
odd problems will turn up if the configuration files are not set up
as expected. If you want to carry your existing configuration to a
new version with minimal work, use ``make oldconfig``, which will
only ask you for the answers to new questions.
- Alternative configuration commands are::
"make config" Plain text interface.
"make menuconfig" Text based color menus, radiolists & dialogs.
"make nconfig" Enhanced text based color menus.
"make xconfig" Qt based configuration tool.
"make gconfig" GTK+ based configuration tool.
"make oldconfig" Default all questions based on the contents of
your existing ./.config file and asking about
new config symbols.
"make olddefconfig"
Like above, but sets new symbols to their default
values without prompting.
"make defconfig" Create a ./.config file by using the default
symbol values from either arch/$ARCH/defconfig
or arch/$ARCH/configs/${PLATFORM}_defconfig,
depending on the architecture.
"make ${PLATFORM}_defconfig"
Create a ./.config file by using the default
symbol values from
arch/$ARCH/configs/${PLATFORM}_defconfig.
Use "make help" to get a list of all available
platforms of your architecture.
"make allyesconfig"
Create a ./.config file by setting symbol
values to 'y' as much as possible.
"make allmodconfig"
Create a ./.config file by setting symbol
values to 'm' as much as possible.
"make allnoconfig" Create a ./.config file by setting symbol
values to 'n' as much as possible.
"make randconfig" Create a ./.config file by setting symbol
values to random values.
"make localmodconfig" Create a config based on current config and
loaded modules (lsmod). Disables any module
option that is not needed for the loaded modules.
To create a localmodconfig for another machine,
store the lsmod of that machine into a file
and pass it in as a LSMOD parameter.
Also, you can preserve modules in certain folders
or kconfig files by specifying their paths in
parameter LMC_KEEP.
target$ lsmod > /tmp/mylsmod
target$ scp /tmp/mylsmod host:/tmp
host$ make LSMOD=/tmp/mylsmod \
LMC_KEEP="drivers/usb:drivers/gpu:fs" \
localmodconfig
The above also works when cross compiling.
"make localyesconfig" Similar to localmodconfig, except it will convert
all module options to built in (=y) options. You can
also preserve modules by LMC_KEEP.
"make kvm_guest.config" Enable additional options for kvm guest kernel
support.
"make xen.config" Enable additional options for xen dom0 guest kernel
support.
"make tinyconfig" Configure the tiniest possible kernel.
You can find more information on using the Linux kernel config tools
in Documentation/kbuild/kconfig.rst.
- NOTES on ``make config``:
- Having unnecessary drivers will make the kernel bigger, and can
under some circumstances lead to problems: probing for a
nonexistent controller card may confuse your other controllers.
- A kernel with math-emulation compiled in will still use the
coprocessor if one is present: the math emulation will just
never get used in that case. The kernel will be slightly larger,
but will work on different machines regardless of whether they
have a math coprocessor or not.
- The "kernel hacking" configuration details usually result in a
bigger or slower kernel (or both), and can even make the kernel
less stable by configuring some routines to actively try to
break bad code to find kernel problems (kmalloc()). Thus you
should probably answer 'n' to the questions for "development",
"experimental", or "debugging" features.
Compiling the kernel
--------------------
- Make sure you have at least gcc 5.1 available.
For more information, refer to :ref:`Documentation/process/changes.rst <changes>`.
- Do a ``make`` to create a compressed kernel image. It is also
possible to do ``make install`` if you have lilo installed to suit the
kernel makefiles, but you may want to check your particular lilo setup first.
To do the actual install, you have to be root, but none of the normal
build should require that. Don't take the name of root in vain.
- If you configured any of the parts of the kernel as ``modules``, you
will also have to do ``make modules_install``.
- Verbose kernel compile/build output:
Normally, the kernel build system runs in a fairly quiet mode (but not
totally silent). However, sometimes you or other kernel developers need
to see compile, link, or other commands exactly as they are executed.
For this, use "verbose" build mode. This is done by passing
``V=1`` to the ``make`` command, e.g.::
make V=1 all
To have the build system also tell the reason for the rebuild of each
target, use ``V=2``. The default is ``V=0``.
- Keep a backup kernel handy in case something goes wrong. This is
especially true for the development releases, since each new release
contains new code which has not been debugged. Make sure you keep a
backup of the modules corresponding to that kernel, as well. If you
are installing a new kernel with the same version number as your
working kernel, make a backup of your modules directory before you
do a ``make modules_install``.
Alternatively, before compiling, use the kernel config option
"LOCALVERSION" to append a unique suffix to the regular kernel version.
LOCALVERSION can be set in the "General Setup" menu.
- In order to boot your new kernel, you'll need to copy the kernel
image (e.g. .../linux/arch/x86/boot/bzImage after compilation)
to the place where your regular bootable kernel is found.
- Booting a kernel directly from a floppy without the assistance of a
bootloader such as LILO, is no longer supported.
If you boot Linux from the hard drive, chances are you use LILO, which
uses the kernel image as specified in the file /etc/lilo.conf. The
kernel image file is usually /vmlinuz, /boot/vmlinuz, /bzImage or
/boot/bzImage. To use the new kernel, save a copy of the old image
and copy the new image over the old one. Then, you MUST RERUN LILO
to update the loading map! If you don't, you won't be able to boot
the new kernel image.
Reinstalling LILO is usually a matter of running /sbin/lilo.
You may wish to edit /etc/lilo.conf to specify an entry for your
old kernel image (say, /vmlinux.old) in case the new one does not
work. See the LILO docs for more information.
After reinstalling LILO, you should be all set. Shutdown the system,
reboot, and enjoy!
If you ever need to change the default root device, video mode,
etc. in the kernel image, use your bootloader's boot options
where appropriate. No need to recompile the kernel to change
these parameters.
- Reboot with the new kernel and enjoy.
If something goes wrong
-----------------------
If you have problems that seem to be due to kernel bugs, please follow the
instructions at 'Documentation/admin-guide/reporting-issues.rst'.
Hints on understanding kernel bug reports are in
'Documentation/admin-guide/bug-hunting.rst'. More on debugging the kernel
with gdb is in 'Documentation/dev-tools/gdb-kernel-debugging.rst' and
'Documentation/dev-tools/kgdb.rst'.
535a265d7f