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docs: RCU: Convert torture.txt to ReST
- Add a SPDX header;
- Adjust document and section titles;
- Some whitespace fixes and new line breaks;
- Mark literal blocks as such;
- Add it to RCU/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
authored by
Mauro Carvalho Chehab
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Paul E. McKenney
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Documentation/RCU/index.rst
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Documentation/RCU/torture.txt
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.. SPDX-License-Identifier: GPL-2.0
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==========================
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RCU Torture Test Operation
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==========================
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CONFIG_RCU_TORTURE_TEST
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=======================
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The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
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implementations. It creates an rcutorture kernel module that can
···
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Module parameters are prefixed by "rcutorture." in
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Documentation/admin-guide/kernel-parameters.txt.
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OUTPUT
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Output
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======
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The statistics output is as follows:
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The statistics output is as follows::
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rcu-torture:--- Start of test: nreaders=16 nfakewriters=4 stat_interval=30 verbose=0 test_no_idle_hz=1 shuffle_interval=3 stutter=5 irqreader=1 fqs_duration=0 fqs_holdoff=0 fqs_stutter=3 test_boost=1/0 test_boost_interval=7 test_boost_duration=4
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rcu-torture: rtc: (null) ver: 155441 tfle: 0 rta: 155441 rtaf: 8884 rtf: 155440 rtmbe: 0 rtbe: 0 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 3055767
···
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The entries are as follows:
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o "rtc": The hexadecimal address of the structure currently visible
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* "rtc": The hexadecimal address of the structure currently visible
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to readers.
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o "ver": The number of times since boot that the RCU writer task
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* "ver": The number of times since boot that the RCU writer task
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has changed the structure visible to readers.
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o "tfle": If non-zero, indicates that the "torture freelist"
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* "tfle": If non-zero, indicates that the "torture freelist"
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containing structures to be placed into the "rtc" area is empty.
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This condition is important, since it can fool you into thinking
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that RCU is working when it is not. :-/
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o "rta": Number of structures allocated from the torture freelist.
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* "rta": Number of structures allocated from the torture freelist.
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o "rtaf": Number of allocations from the torture freelist that have
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* "rtaf": Number of allocations from the torture freelist that have
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failed due to the list being empty. It is not unusual for this
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to be non-zero, but it is bad for it to be a large fraction of
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the value indicated by "rta".
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o "rtf": Number of frees into the torture freelist.
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* "rtf": Number of frees into the torture freelist.
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o "rtmbe": A non-zero value indicates that rcutorture believes that
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* "rtmbe": A non-zero value indicates that rcutorture believes that
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rcu_assign_pointer() and rcu_dereference() are not working
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correctly. This value should be zero.
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o "rtbe": A non-zero value indicates that one of the rcu_barrier()
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* "rtbe": A non-zero value indicates that one of the rcu_barrier()
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family of functions is not working correctly.
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o "rtbke": rcutorture was unable to create the real-time kthreads
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* "rtbke": rcutorture was unable to create the real-time kthreads
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used to force RCU priority inversion. This value should be zero.
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o "rtbre": Although rcutorture successfully created the kthreads
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* "rtbre": Although rcutorture successfully created the kthreads
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used to force RCU priority inversion, it was unable to set them
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to the real-time priority level of 1. This value should be zero.
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o "rtbf": The number of times that RCU priority boosting failed
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* "rtbf": The number of times that RCU priority boosting failed
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to resolve RCU priority inversion.
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o "rtb": The number of times that rcutorture attempted to force
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* "rtb": The number of times that rcutorture attempted to force
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an RCU priority inversion condition. If you are testing RCU
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priority boosting via the "test_boost" module parameter, this
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value should be non-zero.
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o "nt": The number of times rcutorture ran RCU read-side code from
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* "nt": The number of times rcutorture ran RCU read-side code from
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within a timer handler. This value should be non-zero only
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if you specified the "irqreader" module parameter.
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o "Reader Pipe": Histogram of "ages" of structures seen by readers.
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* "Reader Pipe": Histogram of "ages" of structures seen by readers.
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If any entries past the first two are non-zero, RCU is broken.
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And rcutorture prints the error flag string "!!!" to make sure
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you notice. The age of a newly allocated structure is zero,
···
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RCU. If you want to see what it looks like when broken, break
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it yourself. ;-)
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o "Reader Batch": Another histogram of "ages" of structures seen
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* "Reader Batch": Another histogram of "ages" of structures seen
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by readers, but in terms of counter flips (or batches) rather
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than in terms of grace periods. The legal number of non-zero
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entries is again two. The reason for this separate view is that
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it is sometimes easier to get the third entry to show up in the
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"Reader Batch" list than in the "Reader Pipe" list.
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o "Free-Block Circulation": Shows the number of torture structures
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* "Free-Block Circulation": Shows the number of torture structures
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that have reached a given point in the pipeline. The first element
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should closely correspond to the number of structures allocated,
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the second to the number that have been removed from reader view,
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Different implementations of RCU can provide implementation-specific
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additional information. For example, Tree SRCU provides the following
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additional line:
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additional line::
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srcud-torture: Tree SRCU per-CPU(idx=0): 0(35,-21) 1(-4,24) 2(1,1) 3(-26,20) 4(28,-47) 5(-9,4) 6(-10,14) 7(-14,11) T(1,6)
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···
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"old" and "current" values to the underlying array, and is useful for
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debugging. The final "T" entry contains the totals of the counters.
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USAGE ON SPECIFIC KERNEL BUILDS
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Usage on Specific Kernel Builds
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===============================
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It is sometimes desirable to torture RCU on a specific kernel build,
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for example, when preparing to put that kernel build into production.
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In that case, the kernel should be built with CONFIG_RCU_TORTURE_TEST=m
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so that the test can be started using modprobe and terminated using rmmod.
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For example, the following script may be used to torture RCU:
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For example, the following script may be used to torture RCU::
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#!/bin/sh
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···
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were no RCU failures, CPU-hotplug problems were detected.
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USAGE ON MAINLINE KERNELS
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Usage on Mainline Kernels
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=========================
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When using rcutorture to test changes to RCU itself, it is often
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necessary to build a number of kernels in order to test that change
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--configs argument to kvm.sh as follows: "--configs 'SRCU-N SRCU-P'".
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Large systems can run multiple copies of of the full set of scenarios,
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for example, a system with 448 hardware threads can run five instances
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of the full set concurrently. To make this happen:
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of the full set concurrently. To make this happen::
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kvm.sh --cpus 448 --configs '5*CFLIST'
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Alternatively, such a system can run 56 concurrent instances of a single
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eight-CPU scenario:
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eight-CPU scenario::
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kvm.sh --cpus 448 --configs '56*TREE04'
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Or 28 concurrent instances of each of two eight-CPU scenarios:
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Or 28 concurrent instances of each of two eight-CPU scenarios::
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kvm.sh --cpus 448 --configs '28*TREE03 28*TREE04'
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···
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using the --bootargs parameter discussed below.
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Sometimes additional debugging is useful, and in such cases the --kconfig
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parameter to kvm.sh may be used, for example, "--kconfig 'CONFIG_KASAN=y'".
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parameter to kvm.sh may be used, for example, ``--kconfig 'CONFIG_KASAN=y'``.
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Kernel boot arguments can also be supplied, for example, to control
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rcutorture's module parameters. For example, to test a change to RCU's
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CPU stall-warning code, use "--bootargs 'rcutorture.stall_cpu=30'".
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This will of course result in the scripting reporting a failure, namely
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the resuling RCU CPU stall warning. As noted above, reducing memory may
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require disabling rcutorture's callback-flooding tests:
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require disabling rcutorture's callback-flooding tests::
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kvm.sh --cpus 448 --configs '56*TREE04' --memory 128M \
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--bootargs 'rcutorture.fwd_progress=0'
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to a file. The build products and console output of each run is kept in
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tools/testing/selftests/rcutorture/res in timestamped directories. A
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given directory can be supplied to kvm-find-errors.sh in order to have
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it cycle you through summaries of errors and full error logs. For example:
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it cycle you through summaries of errors and full error logs. For example::
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tools/testing/selftests/rcutorture/bin/kvm-find-errors.sh \
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tools/testing/selftests/rcutorture/res/2020.01.20-15.54.23
···
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The most frequently used files in each per-scenario-run directory are:
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.config: This file contains the Kconfig options.
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.config:
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This file contains the Kconfig options.
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Make.out: This contains build output for a specific scenario.
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Make.out:
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This contains build output for a specific scenario.
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console.log: This contains the console output for a specific scenario.
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console.log:
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This contains the console output for a specific scenario.
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This file may be examined once the kernel has booted, but
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it might not exist if the build failed.
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vmlinux: This contains the kernel, which can be useful with tools like
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vmlinux:
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This contains the kernel, which can be useful with tools like
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objdump and gdb.
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A number of additional files are available, but are less frequently used.
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Many are intended for debugging of rcutorture itself or of its scripting.
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As of v5.4, a successful run with the default set of scenarios produces
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the following summary at the end of the run on a 12-CPU system:
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the following summary at the end of the run on a 12-CPU system::
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SRCU-N ------- 804233 GPs (148.932/s) [srcu: g10008272 f0x0 ]
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SRCU-P ------- 202320 GPs (37.4667/s) [srcud: g1809476 f0x0 ]
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SRCU-t ------- 1122086 GPs (207.794/s) [srcu: g0 f0x0 ]
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SRCU-u ------- 1111285 GPs (205.794/s) [srcud: g1 f0x0 ]
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TASKS01 ------- 19666 GPs (3.64185/s) [tasks: g0 f0x0 ]
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TASKS02 ------- 20541 GPs (3.80389/s) [tasks: g0 f0x0 ]
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TASKS03 ------- 19416 GPs (3.59556/s) [tasks: g0 f0x0 ]
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TINY01 ------- 836134 GPs (154.84/s) [rcu: g0 f0x0 ] n_max_cbs: 34198
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TINY02 ------- 850371 GPs (157.476/s) [rcu: g0 f0x0 ] n_max_cbs: 2631
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TREE01 ------- 162625 GPs (30.1157/s) [rcu: g1124169 f0x0 ]
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TREE02 ------- 333003 GPs (61.6672/s) [rcu: g2647753 f0x0 ] n_max_cbs: 35844
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TREE03 ------- 306623 GPs (56.782/s) [rcu: g2975325 f0x0 ] n_max_cbs: 1496497
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CPU count limited from 16 to 12
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TREE04 ------- 246149 GPs (45.5831/s) [rcu: g1695737 f0x0 ] n_max_cbs: 434961
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TREE05 ------- 314603 GPs (58.2598/s) [rcu: g2257741 f0x2 ] n_max_cbs: 193997
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TREE07 ------- 167347 GPs (30.9902/s) [rcu: g1079021 f0x0 ] n_max_cbs: 478732
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CPU count limited from 16 to 12
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TREE09 ------- 752238 GPs (139.303/s) [rcu: g13075057 f0x0 ] n_max_cbs: 99011
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SRCU-N ------- 804233 GPs (148.932/s) [srcu: g10008272 f0x0 ]
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SRCU-P ------- 202320 GPs (37.4667/s) [srcud: g1809476 f0x0 ]
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SRCU-t ------- 1122086 GPs (207.794/s) [srcu: g0 f0x0 ]
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SRCU-u ------- 1111285 GPs (205.794/s) [srcud: g1 f0x0 ]
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TASKS01 ------- 19666 GPs (3.64185/s) [tasks: g0 f0x0 ]
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TASKS02 ------- 20541 GPs (3.80389/s) [tasks: g0 f0x0 ]
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TASKS03 ------- 19416 GPs (3.59556/s) [tasks: g0 f0x0 ]
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TINY01 ------- 836134 GPs (154.84/s) [rcu: g0 f0x0 ] n_max_cbs: 34198
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TINY02 ------- 850371 GPs (157.476/s) [rcu: g0 f0x0 ] n_max_cbs: 2631
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TREE01 ------- 162625 GPs (30.1157/s) [rcu: g1124169 f0x0 ]
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TREE02 ------- 333003 GPs (61.6672/s) [rcu: g2647753 f0x0 ] n_max_cbs: 35844
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TREE03 ------- 306623 GPs (56.782/s) [rcu: g2975325 f0x0 ] n_max_cbs: 1496497
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CPU count limited from 16 to 12
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TREE04 ------- 246149 GPs (45.5831/s) [rcu: g1695737 f0x0 ] n_max_cbs: 434961
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TREE05 ------- 314603 GPs (58.2598/s) [rcu: g2257741 f0x2 ] n_max_cbs: 193997
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TREE07 ------- 167347 GPs (30.9902/s) [rcu: g1079021 f0x0 ] n_max_cbs: 478732
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CPU count limited from 16 to 12
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TREE09 ------- 752238 GPs (139.303/s) [rcu: g13075057 f0x0 ] n_max_cbs: 99011
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Documentation/locking/locktorture.rst
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Documentation/locking/locktorture.rst
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MAINTAINERS
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MAINTAINERS
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F: Documentation/RCU/
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F: include/linux/rcu*
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X: include/linux/srcu*.h
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X: kernel/rcu/srcu*.c
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···
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L: linux-kernel@vger.kernel.org
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S: Supported
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T: git git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
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F: Documentation/RCU/torture.rst
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F: kernel/rcu/rcutorture.c