The current rcu_scale_writer() asynchronous grace-period testing uses a
per-CPU counter to track the number of outstanding callbacks. This is
subject to CPU-imbalance errors when tasks migrate from one CPU to another
between the time that the counter is incremented and the callback is
queued, and additionally in kernels configured such that callbacks can
be invoked on some CPU other than the one that queued it.
This commit therefore arranges for per-task callback counts, thus avoiding
any issues with migration of either tasks or callbacks.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Currently, if someone modprobes and rmmods rcuscale successfully, but
the next run errors out during the modprobe, non-NULL pointers to freed
memory will remain. If the run after that also errors out during the
modprobe, there will be double-free bugs.
This commit therefore NULLs out top-level pointers to memory that has
just been freed.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The rcu_scale_writer() function needs only a fixed number of rcu_head
structures per kthread, which means that a trivial allocator suffices.
This commit therefore uses an llist-based allocator using a fixed array of
structures per kthread. This allows aggressive testing of RCU performance
without stressing the slab allocators.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Under some conditions, kmalloc(GFP_KERNEL) allocations have been
observed to repeatedly fail. This situation has been observed to
cause one of the rcu_scale_writer() instances to loop indefinitely
retrying memory allocation for an asynchronous grace-period primitive.
The problem is that if memory is short, all the other instances will
allocate all available memory before the looping task is awakened from
its rcu_barrier*() call. This in turn results in hangs, so that rcuscale
fails to complete.
This commit therefore removes the tight retry loop, so that when this
condition occurs, the affected task is still passing through the full
loop with its full set of termination checks. This spreads the risk
of indefinite memory-allocation retry failures across all instances of
rcu_scale_writer() tasks, which in turn prevents the hangs.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit causes all writer tasks to provide a brief report after a
hang has been reported, spaced at one-second intervals.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Currently, if the rcuscale module's async module parameter is specified
for RCU implementations that do not have async primitives such as RCU
Tasks Rude (which now lacks a call_rcu_tasks_rude() function), there
will be a series of splats due to calls to a NULL pointer. This commit
therefore warns of this situation, but switches to non-async testing.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit uses the new rcu_tasks_torture_stats_print(),
rcu_tasks_trace_torture_stats_print(), and
rcu_tasks_rude_torture_stats_print() functions in order to provide
detailed diagnostics on grace-period, callback, and barrier state when
rcu_scale_writer() hangs.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit adds a .stats function pointer to the rcu_scale_ops structure,
and if this is non-NULL, it is invoked after stack traces are dumped in
response to a rcu_scale_writer() stall.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit improves debuggability by dumping the stacks of
rcu_scale_writer() instances that have not completed in a reasonable
timeframe. These stacks are dumped remotely, but they will be accurate
in the thus-far common case where the stalled rcu_scale_writer() instances
are blocked.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This whitespace-only commit fuses a few lines of code, taking advantage
of the newish 100-character-per-line limit to save a few lines of code.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The call_rcu_tasks_rude() and rcu_barrier_tasks_rude() APIs are currently
unused. Furthermore, the idea is to get rid of RCU Tasks Rude entirely
once all architectures have their deep-idle and entry/exit code correctly
marked as inline or noinstr. As a step towards this goal, this commit
therefore removes these two functions from rcuscale testing.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Fix the following 'make W=1' warnings:
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/rcu/rcutorture.o
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/rcu/rcuscale.o
WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/rcu/refscale.o
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The variable name jiffies_till_flush is too generic and therefore:
* It may shadow a global variable
* It doesn't tell on what it operates
Make the name more precise, along with the related APIs.
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Both the CONFIG_TASKS_RCU and CONFIG_TASKS_RUDE_RCU options
are broken when RCU_TINY is enabled as well, as some functions
are missing a declaration.
In file included from kernel/rcu/update.c:649:
kernel/rcu/tasks.h:1271:21: error: no previous prototype for 'get_rcu_tasks_rude_gp_kthread' [-Werror=missing-prototypes]
1271 | struct task_struct *get_rcu_tasks_rude_gp_kthread(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/rcu/rcuscale.c:330:27: error: 'get_rcu_tasks_rude_gp_kthread' undeclared here (not in a function); did you mean 'get_rcu_tasks_trace_gp_kthread'?
330 | .rso_gp_kthread = get_rcu_tasks_rude_gp_kthread,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| get_rcu_tasks_trace_gp_kthread
In file included from /home/arnd/arm-soc/kernel/rcu/update.c:649:
kernel/rcu/tasks.h:1113:21: error: no previous prototype for 'get_rcu_tasks_gp_kthread' [-Werror=missing-prototypes]
1113 | struct task_struct *get_rcu_tasks_gp_kthread(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~
Also, building with CONFIG_TASKS_RUDE_RCU but not CONFIG_TASKS_RCU is
broken because of some missing stub functions:
kernel/rcu/rcuscale.c:322:27: error: 'tasks_scale_read_lock' undeclared here (not in a function); did you mean 'srcu_scale_read_lock'?
322 | .readlock = tasks_scale_read_lock,
| ^~~~~~~~~~~~~~~~~~~~~
| srcu_scale_read_lock
kernel/rcu/rcuscale.c:323:27: error: 'tasks_scale_read_unlock' undeclared here (not in a function); did you mean 'srcu_scale_read_unlock'?
323 | .readunlock = tasks_scale_read_unlock,
| ^~~~~~~~~~~~~~~~~~~~~~~
| srcu_scale_read_unlock
Move the declarations outside of the RCU_TINY #ifdef and duplicate the
shared stub functions to address all of the above.
Fixes: 88d7ff818f0ce ("rcuscale: Add RCU Tasks Rude testing")
Fixes: 755f1c5eb416b ("rcuscale: Measure RCU Tasks Trace grace-period kthread CPU time")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit causes RCU Tasks Trace to output the CPU time consumed by
its grace-period kthread. The CPU time is whatever is in the designated
task's current->stime field, and thus is controlled by whatever CPU-time
accounting scheme is in effect.
This output appears in microseconds as follows on the console:
rcu_scale: Grace-period kthread CPU time: 42367.037
[ paulmck: Apply Willy Tarreau feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the ability to output the CPU time consumed by the
grace-period kthread for the RCU variant under test. The CPU time is
whatever is in the designated task's current->stime field, and thus is
controlled by whatever CPU-time accounting scheme is in effect.
This output appears in microseconds as follows on the console:
rcu_scale: Grace-period kthread CPU time: 42367.037
[ paulmck: Apply feedback from Stephen Rothwell and kernel test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
By default, rcuscale collects only 100 points of data per writer, but
arranging for all kthreads to be actively collecting (if not recording)
data during the time that any kthread might be recording. This works
well, but does not allow much time to bring external performance tools
to bear. This commit therefore adds a minruntime module parameter
that specifies a minimum data-collection interval in seconds.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Some workloads do isolated RCU work, and this can affect operation
latencies. This commit therefore adds a writer_holdoff_jiffies module
parameter that causes writers to block for the specified number of
jiffies between each pair of consecutive write-side operations.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This code-movement-only commit moves the rcu_scale_cleanup() and
rcu_scale_shutdown() functions to follow kfree_scale_cleanup().
This is code movement is in preparation for a bug-fix patch that invokes
kfree_scale_cleanup() from rcu_scale_cleanup().
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
The kfree_rcu() and kvfree_rcu() macros' single-argument forms are
deprecated. Therefore switch to the new kfree_rcu_mightsleep() and
kvfree_rcu_mightsleep() variants. The goal is to avoid accidental use
of the single-argument forms, which can introduce functionality bugs in
atomic contexts and latency bugs in non-atomic contexts.
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
The rcu_scale_shutdown() and kfree_scale_shutdown() kthreads/functions
use wait_event() to wait for the rcuscale test to complete. However,
each updater thread in such a test waits for at least 100 grace periods.
If each grace period takes more than 1.2 seconds, which is long, but
not insanely so, this can trigger the hung-task timeout.
This commit therefore replaces those wait_event() calls with calls to
wait_event_idle(), which do not trigger the hung-task timeout.
Reported-by: kernel test robot <yujie.liu@intel.com>
Reported-by: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
rcuscale uses call_rcu() to queue async readers. With recent changes to
save power, the test will have fewer async readers in flight. Use the
call_rcu_hurry() API instead to revert to the old behavior.
[ paulmck: Apply s/call_rcu_flush/call_rcu_hurry/ feedback from Tejun Heo. ]
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds 2 tests to rcuscale. The first one is a startup test
to check whether we are not too lazy or too hard working. The second
one causes kfree_rcu() itself to use call_rcu() and checks memory
pressure. Testing indicates that the new call_rcu() keeps memory pressure
under control roughly as well as does kfree_rcu().
[ paulmck: Apply checkpatch feedback. ]
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Systems built with CONFIG_DEBUG_PREEMPT=y can trigger the following
BUG while running the rcuscale performance test:
BUG: using smp_processor_id() in preemptible [00000000] code: rcu_scale_write/69
CPU: 0 PID: 66 Comm: rcu_scale_write Not tainted 5.18.0-rc7-next-20220517-yoctodev-standard+
caller is debug_smp_processor_id+0x17/0x20
Call Trace:
<TASK>
dump_stack_lvl+0x49/0x5e
dump_stack+0x10/0x12
check_preemption_disabled+0xdf/0xf0
debug_smp_processor_id+0x17/0x20
rcu_scale_writer+0x2b5/0x580
kthread+0x177/0x1b0
ret_from_fork+0x22/0x30
</TASK>
Reproduction method:
runqemu kvm slirp nographic qemuparams="-m 4096 -smp 8" bootparams="isolcpus=2,3
nohz_full=2,3 rcu_nocbs=2,3 rcutree.dump_tree=1 rcuscale.shutdown=false
rcuscale.gp_async=true" -d
The problem is that the rcu_scale_writer() kthreads fail to set the
PF_NO_SETAFFINITY flags, which causes is_percpu_thread() to assume
that the kthread's affinity might change at any time, thus the BUG
noted above.
This commit therefore causes rcu_scale_writer() to set PF_NO_SETAFFINITY
in its kthread's ->flags field, thus preventing this BUG.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks Rude and RCU Tasks Trace. Unless that kernel builds rcuscale,
whether built-in or as a module, in which case these RCU Tasks flavors are
(unnecessarily) built in. This both increases kernel size and increases
the complexity of certain tracing operations. This commit therefore
decouples the presence of rcuscale from the presence of RCU Tasks Rude
and RCU Tasks Trace.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for
RCU Tasks. Unless that kernel builds rcuscale, whether built-in or as
a module, in which case RCU Tasks is (unnecessarily) built. This both
increases kernel size and increases the complexity of certain tracing
operations. This commit therefore decouples the presence of rcuscale
from the presence of RCU Tasks.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Unconditionally log messages corresponding to errors.
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Li Zhijian <zhijianx.li@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
When running rcuscale as a module, any rcu_scale_init() issues will be
reflected in the error code from modprobe or insmod, as the case may be.
However, these error codes are not available when running rcuscale
built-in, for example, when using the kvm.sh script. This commit
therefore adds WARN_ON_ONCE() to allow distinguishing rcu_scale_init()
errors when running rcuscale built-in.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcuscale console output claims N grace periods, numbered from zero
to N, which means that there were really N+1 grace periods. The root
cause of this bug is that rcu_scale_writer() stores the number of the
last grace period (numbered from zero) into writer_n_durations[me]
instead of the number of grace periods. This commit therefore assigns
the actual number of grace periods to writer_n_durations[me], and also
makes the corresponding adjustment to the loop outputting per-grace-period
measurements.
Sample of old console output:
rcu-scale: writer 0 gps: 133
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410
Sample of new console output:
rcu-scale: writer 0 gps: 134
......
rcu-scale: 0 writer-duration: 0 44003961
rcu-scale: 0 writer-duration: 1 32003582
......
rcu-scale: 0 writer-duration: 132 28004391
rcu-scale: 0 writer-duration: 133 27996410
Signed-off-by: Jiangong.Han <jiangong.han@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The single-argument variant of kfree_rcu() is currently not
tested by any member of the rcutoture test suite. This
commit therefore adds rcuscale code to test it. This
testing is controlled by two new boolean module parameters,
kfree_rcu_test_single and kfree_rcu_test_double. If one
is set and the other not, only the corresponding variant
is tested, otherwise both are tested, with the variant to
be tested determined randomly on each invocation.
Both of these module parameters are initialized to false,
so setting either to true will test only that variant.
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If an rcuscale torture-test run is given a bad kvm.sh argument, the
test will complain to the console, which is good. What is bad is that
from the user's perspective, it will just hang for the time specified
by the --duration argument. This commit therefore forces an immediate
kernel shutdown if a rcu_scale_init()-time error occurs, thus avoiding
the appearance of a hang. It also forces a console splat in this case
to clearly indicate the presence of an error.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the ability to test performance and scalability of RCU
Tasks Trace updaters.
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit further avoids conflation of rcuperf with the kernel's perf
feature by renaming kernel/rcu/rcuperf.c to kernel/rcu/rcuscale.c, and
also by similarly renaming the functions and variables inside this file.
This has the side effect of changing the names of the kernel boot
parameters, so kernel-parameters.txt and ver_functions.sh are also
updated. The rcutorture --torture type was also updated from rcuperf
to rcuscale.
[ paulmck: Fix bugs located by Stephen Rothwell. ]
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
