In commit 95433f7263 ("srcu: Begin offloading srcu_struct fields to
srcu_update"), a new struct srcu_usage field was added, but was not
properly initialized. This led to a "spinlock bad magic" BUG when the
SRCU notifier was ever used. This was observed in the MediaTek CCI
devfreq driver on next-20230525. The trimmed stack trace is as follows:
BUG: spinlock bad magic on CPU#4, swapper/0/1
lock: 0xffffff80ff529ac0, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
Call trace:
spin_bug+0xa4/0xe8
do_raw_spin_lock+0xec/0x120
_raw_spin_lock_irqsave+0x78/0xb8
synchronize_srcu+0x3c/0x168
srcu_notifier_chain_unregister+0x5c/0xa0
cpufreq_unregister_notifier+0x94/0xe0
devfreq_passive_event_handler+0x7c/0x3e0
devfreq_remove_device+0x48/0xe8
Add __SRCU_USAGE_INIT() to SRCU_NOTIFIER_INIT() so that srcu_usage gets
initialized properly.
Reported-by: Jon Hunter <jonathanh@nvidia.com>
Fixes: 95433f7263 ("srcu: Begin offloading srcu_struct fields to srcu_update")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc: Sachin Sant <sachinp@linux.ibm.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The qemu argument -enable-kvm is duplicated because the qemu_args bash
variable in kvm-test-1-run.sh already provides it. This commit therefore
removes the ppc64-specific copy in functions.sh.
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
If you build a kernel with CONFIG_PREEMPTION=n and CONFIG_PREEMPT_COUNT=y,
then run the rcutorture tests specifying stalls as follows:
runqemu kvm slirp nographic qemuparams="-m 1024 -smp 4" \
bootparams="console=ttyS0 rcutorture.stall_cpu=30 \
rcutorture.stall_no_softlockup=1 rcutorture.stall_cpu_block=1" -d
The tests will produce the following splat:
[ 10.841071] rcu-torture: rcu_torture_stall begin CPU stall
[ 10.841073] rcu_torture_stall start on CPU 3.
[ 10.841077] BUG: scheduling while atomic: rcu_torture_sta/66/0x0000000
....
[ 10.841108] Call Trace:
[ 10.841110] <TASK>
[ 10.841112] dump_stack_lvl+0x64/0xb0
[ 10.841118] dump_stack+0x10/0x20
[ 10.841121] __schedule_bug+0x8b/0xb0
[ 10.841126] __schedule+0x2172/0x2940
[ 10.841157] schedule+0x9b/0x150
[ 10.841160] schedule_timeout+0x2e8/0x4f0
[ 10.841192] schedule_timeout_uninterruptible+0x47/0x50
[ 10.841195] rcu_torture_stall+0x2e8/0x300
[ 10.841199] kthread+0x175/0x1a0
[ 10.841206] ret_from_fork+0x2c/0x50
This is because the rcutorture.stall_cpu_block=1 module parameter causes
rcu_torture_stall() to invoke schedule_timeout_uninterruptible() within
an RCU read-side critical section. This in turn results in a quiescent
state (which prevents the stall) and a sleep in an atomic context (which
produces the above splat).
Although this code is operating as designed, the design has proven to
be counterintuitive to many. This commit therefore updates the description
in kernel-parameters.txt accordingly.
[ paulmck: Apply Joel Fernandes feedback. ]
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
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 BUSTED-BOOST and TREE03 scenarios specify a mythical tree.use_softirq
module parameter, which means a failure to get full test coverage. This
commit therefore corrects the name to rcutree.use_softirq.
Fixes: e2b949d543 ("rcutorture: Make TREE03 use real-time tree.use_softirq setting")
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
This commit adds a long_hold module parameter to allow testing diagnostics
for excessive lock-hold times. Also adjust torture_param() invocations
for longer line length while in the area.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Callbacks can only be queued as lazy on NOCB CPUs, therefore iterating
over the NOCB mask is enough for both counting and scanning. Just lock
the mostly uncontended barrier mutex on counting as well in order to
keep rcu_nocb_mask stable.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_tasks_invoke_cbs() function relies on queue_work_on() to silently
fall back to WORK_CPU_UNBOUND when the specified CPU is offline. However,
the queue_work_on() function's silent fallback mechanism relies on that
CPU having been online at some time in the past. When queue_work_on()
is passed a CPU that has never been online, workqueue lockups ensue,
which can be bad for your kernel's general health and well-being.
This commit therefore checks whether a given CPU has ever been online,
and, if not substitutes WORK_CPU_UNBOUND in the subsequent call to
queue_work_on(). Why not simply omit the queue_work_on() call entirely?
Because this function is flooding callback-invocation notifications
to all CPUs, and must deal with possibilities that include a sparse
cpu_possible_mask.
This commit also moves the setting of the rcu_data structure's
->beenonline field to rcu_cpu_starting(), which executes on the
incoming CPU before that CPU has ever enabled interrupts. This ensures
that the required workqueues are present. In addition, because the
incoming CPU has not yet enabled its interrupts, there cannot yet have
been any softirq handlers running on this CPU, which means that the
WARN_ON_ONCE(!rdp->beenonline) within the RCU_SOFTIRQ handler cannot
have triggered yet.
Fixes: d363f833c6 ("rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations")
Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, rcu_cpu_starting() is written so that it might be invoked
with interrupts enabled. However, it is always called when interrupts
are disabled, either by rcu_init(), notify_cpu_starting(), or from a
call point prior to the call to notify_cpu_starting().
But why bother requiring that interrupts be disabled? The purpose is
to allow the rcu_data structure's ->beenonline flag to be set after all
early processing has completed for the incoming CPU, thus allowing this
flag to be used to determine when workqueues have been set up for the
incoming CPU, while still allowing this flag to be used as a diagnostic
within rcu_core().
This commit therefore makes rcu_cpu_starting() rely on interrupts being
disabled.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_data structure's ->rcu_cpu_has_work field can be modified by
any CPU attempting to wake up the rcuc kthread. Therefore, this commit
marks accesses to this field from the rcu_cpu_kthread() function.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The per-CPU rcu_data structure's ->cpu_no_qs.b.exp field is updated
only on the instance corresponding to the current CPU, but can be read
more widely. Unmarked accesses are OK from the corresponding CPU, but
only if interrupts are disabled, given that interrupt handlers can and
do modify this field.
Unfortunately, although the load from rcu_preempt_deferred_qs() is always
carried out from the corresponding CPU, interrupts are not necessarily
disabled. This commit therefore upgrades this load to READ_ONCE.
Similarly, the diagnostic access from synchronize_rcu_expedited_wait()
might run with interrupts disabled and from some other CPU. This commit
therefore marks this load with data_race().
Finally, the C-language access in rcu_preempt_ctxt_queue() is OK as
is because interrupts are disabled and this load is always from the
corresponding CPU. This commit adds a comment giving the rationale for
this access being safe.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, if there are more than 100 ready-to-invoke RCU callbacks queued
on a given CPU, the rcu_do_batch() function sets a timeout for invocation
of the series. This timeout defaulting to three milliseconds, and may
be adjusted using the rcutree.rcu_resched_ns kernel boot parameter.
This timeout is checked using local_clock(), but the overhead of this
function combined with the common-case very small callback-invocation
overhead means that local_clock() is checked every 32nd invocation.
This works well except for longer-than average callbacks. For example,
a series of 500-microsecond-duration callbacks means that local_clock()
is checked only once every 16 milliseconds, which makes it difficult to
enforce a three-millisecond timeout.
This commit therefore adds a Kconfig option RCU_DOUBLE_CHECK_CB_TIME
that enables backup timeout checking using the coarser grained but
lighter weight jiffies. If the jiffies counter detects a timeout,
then local_clock() is consulted even if this is not the 32nd callback.
This prevents the aforementioned 16-millisecond latency blow.
Reported-by: Domas Mituzas <dmituzas@meta.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, a callback-invocation time limit is enforced only for
callbacks invoked from the softirq environment, the rationale being
that when callbacks are instead invoked from rcuc and rcuoc kthreads,
these callbacks cannot be holding up other softirq vectors.
Which is in fact true. However, if an rcuc kthread spends too much time
invoking callbacks, it can delay quiescent-state reports from its CPU,
which can also be a problem.
This commit therefore applies the callback-invocation time limit to
callback invocation from the rcuc kthreads as well as from softirq.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Since there are now exactly _zero_ users of RCU_NONIDLE(), make it go
away before someone else decides to (ab)use it.
[ paulmck: Remove extraneous whitespace. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit uses rtp->name instead of __func__ and outputs the value
of rcu_task_cb_adjust, thus reducing console-log output.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The ->lazy_len is only checked locklessly. Recheck again under the
->nocb_lock to avoid spending more time on flushing/waking if not
necessary. The ->lazy_len can still increment concurrently (from 1 to
infinity) but under the ->nocb_lock we at least know for sure if there
are lazy callbacks at all (->lazy_len > 0).
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The shrinker resets the lazy callbacks counter in order to trigger the
pending lazy queue flush though the rcuog kthread. The counter reset is
protected by the ->nocb_lock against concurrent accesses...except
for one of them. Here is a list of existing synchronized readers/writer:
1) The first lazy enqueuer (incrementing ->lazy_len to 1) does so under
->nocb_lock and ->nocb_bypass_lock.
2) The further lazy enqueuers (incrementing ->lazy_len above 1) do so
under ->nocb_bypass_lock _only_.
3) The lazy flush checks and resets to 0 under ->nocb_lock and
->nocb_bypass_lock.
The shrinker protects its ->lazy_len reset against cases 1) and 3) but
not against 2). As such, setting ->lazy_len to 0 under the ->nocb_lock
may be cancelled right away by an overwrite from an enqueuer, leading
rcuog to ignore the flush.
To avoid that, use the proper bypass flush API which takes care of all
those details.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The shrinker may run concurrently with callbacks (de-)offloading. As
such, calling rcu_nocb_lock() is very dangerous because it does a
conditional locking. The worst outcome is that rcu_nocb_lock() doesn't
lock but rcu_nocb_unlock() eventually unlocks, or the reverse, creating
an imbalance.
Fix this with protecting against (de-)offloading using the barrier mutex.
Although if the barrier mutex is contended, which should be rare, then
step aside so as not to trigger a mutex VS allocation
dependency chain.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If the rcutree.rcu_min_cached_objs kernel boot parameter is set to zero,
then krcp->page_cache_work will never be triggered to fill page cache.
In addition, the put_cached_bnode() will not fill page cache. As a
result krcp->bkvcache will always be empty, so there is no need to acquire
krcp->lock to get page from krcp->bkvcache. This commit therefore makes
drain_page_cache() return immediately if the rcu_min_cached_objs is zero.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
When the fill_page_cache_func() function is invoked, it assumes that
the cache of pages is completely empty. However, there can be some time
between triggering execution of this function and its actual invocation.
During this time, kfree_rcu_work() might run, and might fill in part or
all of this cache of pages, thus invalidating the fill_page_cache_func()
function's assumption.
This will not overfill the cache because put_cached_bnode() will reject
the extra page. However, it will result in a needless allocation and
freeing of one extra page, which might not be helpful under lowish-memory
conditions.
This commit therefore causes the fill_page_cache_func() to explicitly
account for pages that have been placed into the cache shortly before
it starts running.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
By default the cache size is 5 pages per CPU, but it can be disabled at
boot time by setting the rcu_min_cached_objs to zero. When that happens,
the current code will uselessly set an hrtimer to schedule refilling this
cache with zero pages. This commit therefore streamlines this process
by simply refusing the set the hrtimer when rcu_min_cached_objs is zero.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The add_ptr_to_bulk_krc_lock() function is invoked to allocate a new
kfree_rcu() page, also known as a kvfree_rcu_bulk_data structure.
The kfree_rcu_cpu structure's lock is used to protect this operation,
except that this lock must be momentarily dropped when allocating memory.
It is clearly important that the lock that is reacquired be the same
lock that was acquired initially via krc_this_cpu_lock().
Unfortunately, this same krc_this_cpu_lock() function is used to
re-acquire this lock, and if the task migrated to some other CPU during
the memory allocation, this will result in the kvfree_rcu_bulk_data
structure being added to the wrong CPU's kfree_rcu_cpu structure.
This commit therefore replaces that second call to krc_this_cpu_lock()
with raw_spin_lock_irqsave() in order to explicitly acquire the lock on
the correct kfree_rcu_cpu structure, thus keeping things straight even
when the task migrates.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If kvfree_rcu_bulk() sees that the required grace period has failed to
elapse, it leaks the memory because readers might still be using it.
But in that case, the debug-objects subsystem still marks the relevant
structures as having been freed, even though they are instead being
leaked.
This commit fixes this mismatch by invoking debug_rcu_bhead_unqueue()
only when we are actually going to free the objects.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Under low-memory conditions, kvfree_rcu() will use each object's
rcu_head structure to queue objects in a singly linked list headed by
the kfree_rcu_cpu structure's ->head field. This list is passed to
call_rcu() as a unit, but there is no indication of which grace period
this list needs to wait for. This in turn prevents adding debug checks
in the kfree_rcu_work() as was done for the two page-of-pointers channels
in the kfree_rcu_cpu structure.
This commit therefore adds a ->head_free_gp_snap field to the
kfree_rcu_cpu_work structure to record this grace-period number. It also
adds a WARN_ON_ONCE() to kfree_rcu_monitor() that checks to make sure
that the required grace period has in fact elapsed.
[ paulmck: Fix kerneldoc issue raised by Stephen Rothwell. ]
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds debugging checks to verify that the required RCU
grace period has elapsed for each kvfree_rcu_bulk_data structure that
arrives at the kvfree_rcu_bulk() function. These checks make use
of that structure's ->gp_snap field, which has been upgraded from an
unsigned long to an rcu_gp_oldstate structure. This upgrade reduces
the chances of false positives to nearly zero, even on 32-bit systems,
for which this structure carries 64 bits of state.
Cc: Ziwei Dai <ziwei.dai@unisoc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The kvfree_rcu() and kfree_rcu() APIs are hazardous in that if you forget
the second argument, it works, but might sleep. This sleeping can be a
correctness bug from atomic contexts, and even in non-atomic contexts it
might introduce unacceptable latencies. This commit therefore removes the
single-argument kvfree_rcu() and kfree_rcu() macros. Code that would have
previously used these single-argument kvfree_rcu() and kfree_rcu() macros
should instead use kvfree_rcu_mightsleep() or kfree_rcu_mightsleep().
[ paulmck: Apply Joel Fernandes feedback. ]
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>
This commit removes extraneous parentheses from srcu_read_lock(),
srcu_read_lock_nmisafe(), srcu_read_unlock(), and
srcu_read_unlock_nmisafe(). Looks like someone was once a macro.
Cc: Christoph Hellwig <hch@lst.de>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Tested-by: "Zhang, Qiang1" <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds kernel-parameters.txt documentation for the
rcutree.rcu_resched_ns module parameter.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Pull perf tool updates from Arnaldo Carvalho de Melo:
"Third version of perf tool updates, with the build problems with with
using a 'vmlinux.h' generated from the main build fixed, and the bpf
skeleton build disabled by default.
Build:
- Require libtraceevent to build, one can disable it using
NO_LIBTRACEEVENT=1.
It is required for tools like 'perf sched', 'perf kvm', 'perf
trace', etc.
libtraceevent is available in most distros so installing
'libtraceevent-devel' should be a one-time event to continue
building perf as usual.
Using NO_LIBTRACEEVENT=1 produces tooling that is functional and
sufficient for lots of users not interested in those libtraceevent
dependent features.
- Allow Python support in 'perf script' when libtraceevent isn't
linked, as not all features requires it, for instance Intel PT does
not use tracepoints.
- Error if the python interpreter needed for jevents to work isn't
available and NO_JEVENTS=1 isn't set, preventing a build without
support for JSON vendor events, which is a rare but possible
condition. The two check error messages:
$(error ERROR: No python interpreter needed for jevents generation. Install python or build with NO_JEVENTS=1.)
$(error ERROR: Python interpreter needed for jevents generation too old (older than 3.6). Install a newer python or build with NO_JEVENTS=1.)
- Make libbpf 1.0 the minimum required when building with out of
tree, distro provided libbpf.
- Use libsdtc++'s and LLVM's libcxx's __cxa_demangle, a portable C++
demangler, add 'perf test' entry for it.
- Make binutils libraries opt in, as distros disable building with it
due to licensing, they were used for C++ demangling, for instance.
- Switch libpfm4 to opt-out rather than opt-in, if libpfm-devel (or
equivalent) isn't installed, we'll just have a build warning:
Makefile.config:1144: libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev
- Add a feature test for scandirat(), that is not implemented so far
in musl and uclibc, disabling features that need it, such as
scanning for tracepoints in /sys/kernel/tracing/events.
perf BPF filters:
- New feature where BPF can be used to filter samples, for instance:
$ sudo ./perf record -e cycles --filter 'period > 1000' true
$ sudo ./perf script
perf-exec 2273949 546850.708501: 5029 cycles: ffffffff826f9e25 finish_wait+0x5 ([kernel.kallsyms])
perf-exec 2273949 546850.708508: 32409 cycles: ffffffff826f9e25 finish_wait+0x5 ([kernel.kallsyms])
perf-exec 2273949 546850.708526: 143369 cycles: ffffffff82b4cdbf xas_start+0x5f ([kernel.kallsyms])
perf-exec 2273949 546850.708600: 372650 cycles: ffffffff8286b8f7 __pagevec_lru_add+0x117 ([kernel.kallsyms])
perf-exec 2273949 546850.708791: 482953 cycles: ffffffff829190de __mod_memcg_lruvec_state+0x4e ([kernel.kallsyms])
true 2273949 546850.709036: 501985 cycles: ffffffff828add7c tlb_gather_mmu+0x4c ([kernel.kallsyms])
true 2273949 546850.709292: 503065 cycles: 7f2446d97c03 _dl_map_object_deps+0x973 (/usr/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2)
- In addition to 'period' (PERF_SAMPLE_PERIOD), the other
PERF_SAMPLE_ can be used for filtering, and also some other sample
accessible values, from tools/perf/Documentation/perf-record.txt:
Essentially the BPF filter expression is:
<term> <operator> <value> (("," | "||") <term> <operator> <value>)*
The <term> can be one of:
ip, id, tid, pid, cpu, time, addr, period, txn, weight, phys_addr,
code_pgsz, data_pgsz, weight1, weight2, weight3, ins_lat, retire_lat,
p_stage_cyc, mem_op, mem_lvl, mem_snoop, mem_remote, mem_lock,
mem_dtlb, mem_blk, mem_hops
The <operator> can be one of:
==, !=, >, >=, <, <=, &
The <value> can be one of:
<number> (for any term)
na, load, store, pfetch, exec (for mem_op)
l1, l2, l3, l4, cxl, io, any_cache, lfb, ram, pmem (for mem_lvl)
na, none, hit, miss, hitm, fwd, peer (for mem_snoop)
remote (for mem_remote)
na, locked (for mem_locked)
na, l1_hit, l1_miss, l2_hit, l2_miss, any_hit, any_miss, walk, fault (for mem_dtlb)
na, by_data, by_addr (for mem_blk)
hops0, hops1, hops2, hops3 (for mem_hops)
perf lock contention:
- Show lock type with address.
- Track and show mmap_lock, siglock and per-cpu rq_lock with address.
This is done for mmap_lock by following the current->mm pointer:
$ sudo ./perf lock con -abl -- sleep 10
contended total wait max wait avg wait address symbol
...
16344 312.30 ms 2.22 ms 19.11 us ffff8cc702595640
17686 310.08 ms 1.49 ms 17.53 us ffff8cc7025952c0
3 84.14 ms 45.79 ms 28.05 ms ffff8cc78114c478 mmap_lock
3557 76.80 ms 68.75 us 21.59 us ffff8cc77ca3af58
1 68.27 ms 68.27 ms 68.27 ms ffff8cda745dfd70
9 54.53 ms 7.96 ms 6.06 ms ffff8cc7642a48b8 mmap_lock
14629 44.01 ms 60.00 us 3.01 us ffff8cc7625f9ca0
3481 42.63 ms 140.71 us 12.24 us ffffffff937906ac vmap_area_lock
16194 38.73 ms 42.15 us 2.39 us ffff8cd397cbc560
11 38.44 ms 10.39 ms 3.49 ms ffff8ccd6d12fbb8 mmap_lock
1 5.43 ms 5.43 ms 5.43 ms ffff8cd70018f0d8
1674 5.38 ms 422.93 us 3.21 us ffffffff92e06080 tasklist_lock
581 4.51 ms 130.68 us 7.75 us ffff8cc9b1259058
5 3.52 ms 1.27 ms 703.23 us ffff8cc754510070
112 3.47 ms 56.47 us 31.02 us ffff8ccee38b3120
381 3.31 ms 73.44 us 8.69 us ffffffff93790690 purge_vmap_area_lock
255 3.19 ms 36.35 us 12.49 us ffff8d053ce30c80
- Update default map size to 16384.
- Allocate single letter option -M for --map-nr-entries, as it is
proving being frequently used.
- Fix struct rq lock access for older kernels with BPF's CO-RE
(Compile once, run everywhere).
- Fix problems found with MSAn.
perf report/top:
- Add inline information when using --call-graph=fp or lbr, as was
already done to the --call-graph=dwarf callchain mode.
- Improve the 'srcfile' sort key performance by really using an
optimization introduced in 6.2 for the 'srcline' sort key that
avoids calling addr2line for comparision with each sample.
perf sched:
- Make 'perf sched latency/map/replay' to use "sched:sched_waking"
instead of "sched:sched_waking", consistent with 'perf record'
since d566a9c2d4 ("perf sched: Prefer sched_waking event when it
exists").
perf ftrace:
- Make system wide the default target for latency subcommand, run the
following command then generate some network traffic and press
control+C:
# perf ftrace latency -T __kfree_skb
^C
DURATION | COUNT | GRAPH |
0 - 1 us | 27 | ############# |
1 - 2 us | 22 | ########### |
2 - 4 us | 8 | #### |
4 - 8 us | 5 | ## |
8 - 16 us | 24 | ############ |
16 - 32 us | 2 | # |
32 - 64 us | 1 | |
64 - 128 us | 0 | |
128 - 256 us | 0 | |
256 - 512 us | 0 | |
512 - 1024 us | 0 | |
1 - 2 ms | 0 | |
2 - 4 ms | 0 | |
4 - 8 ms | 0 | |
8 - 16 ms | 0 | |
16 - 32 ms | 0 | |
32 - 64 ms | 0 | |
64 - 128 ms | 0 | |
128 - 256 ms | 0 | |
256 - 512 ms | 0 | |
512 - 1024 ms | 0 | |
1 - ... s | 0 | |
#
perf top:
- Add --branch-history (LBR: Last Branch Record) option, just like
already available for 'perf record'.
- Fix segfault in thread__comm_len() where thread->comm was being
used outside thread->comm_lock.
perf annotate:
- Allow configuring objdump and addr2line in ~/.perfconfig., so that
you can use alternative binaries, such as llvm's.
perf kvm:
- Add TUI mode for 'perf kvm stat report'.
Reference counting:
- Add reference count checking infrastructure to check for use after
free, done to the 'cpumap', 'namespaces', 'maps' and 'map' structs,
more to come.
To build with it use -DREFCNT_CHECKING=1 in the make command line
to build tools/perf. Documented at:
https://perf.wiki.kernel.org/index.php/Reference_Count_Checking
- The above caught, for instance, fix, present in this series:
- Fix maps use after put in 'perf test "Share thread maps"':
'maps' is copied from leader, but the leader is put on line 79
and then 'maps' is used to read the reference count below - so
a use after put, with the put of maps happening within
thread__put.
Fixed by reversing the order of puts so that the leader is put
last.
- Also several fixes were made to places where reference counts were
not being held.
- Make this one of the tests in 'make -C tools/perf build-test' to
regularly build test it and to make sure no direct access to the
reference counted structs are made, doing that via accessors to
check the validity of the struct pointer.
ARM64:
- Fix 'perf report' segfault when filtering coresight traces by
sparse lists of CPUs.
- Add support for 'simd' as a sort field for 'perf report', to show
ARM's NEON SIMD's predicate flags: "partial" and "empty".
arm64 vendor events:
- Add N1 metrics.
Intel vendor events:
- Add graniterapids, grandridge and sierraforrest events.
- Refresh events for: alderlake, aldernaken, broadwell, broadwellde,
broadwellx, cascadelakx, haswell, haswellx, icelake, icelakex,
jaketown, meteorlake, knightslanding, sandybridge, sapphirerapids,
silvermont, skylake, tigerlake and westmereep-dp
- Refresh metrics for alderlake-n, broadwell, broadwellde,
broadwellx, haswell, haswellx, icelakex, ivybridge, ivytown and
skylakex.
perf stat:
- Implement --topdown using JSON metrics.
- Add TopdownL1 JSON metric as a default if present, but disable it
for now for some Intel hybrid architectures, a series of patches
addressing this is being reviewed and will be submitted for v6.5.
- Use metrics for --smi-cost.
- Update topdown documentation.
Vendor events (JSON) infrastructure:
- Add support for computing and printing metric threshold values. For
instance, here is one found in thesapphirerapids json file:
{
"BriefDescription": "Percentage of cycles spent in System Management Interrupts.",
"MetricExpr": "((msr@aperf@ - cycles) / msr@aperf@ if msr@smi@ > 0 else 0)",
"MetricGroup": "smi",
"MetricName": "smi_cycles",
"MetricThreshold": "smi_cycles > 0.1",
"ScaleUnit": "100%"
},
- Test parsing metric thresholds with the fake PMU in 'perf test
pmu-events'.
- Support for printing metric thresholds in 'perf list'.
- Add --metric-no-threshold option to 'perf stat'.
- Add rand (reverse and) and has_pmem (optane memory) support to
metrics.
- Sort list of input files to avoid depending on the order from
readdir() helping in obtaining reproducible builds.
S/390:
- Add common metrics: - CPI (cycles per instruction), prbstate (ratio
of instructions executed in problem state compared to total number
of instructions), l1mp (Level one instruction and data cache misses
per 100 instructions).
- Add cache metrics for z13, z14, z15 and z16.
- Add metric for TLB and cache.
ARM:
- Add raw decoding for SPE (Statistical Profiling Extension) v1.3 MTE
(Memory Tagging Extension) and MOPS (Memory Operations) load/store.
Intel PT hardware tracing:
- Add event type names UINTR (User interrupt delivered) and UIRET
(Exiting from user interrupt routine), documented in table 32-50
"CFE Packet Type and Vector Fields Details" in the Intel Processor
Trace chapter of The Intel SDM Volume 3 version 078.
- Add support for new branch instructions ERETS and ERETU.
- Fix CYC timestamps after standalone CBR
ARM CoreSight hardware tracing:
- Allow user to override timestamp and contextid settings.
- Fix segfault in dso lookup.
- Fix timeless decode mode detection.
- Add separate decode paths for timeless and per-thread modes.
auxtrace:
- Fix address filter entire kernel size.
Miscellaneous:
- Fix use-after-free and unaligned bugs in the PLT handling routines.
- Use zfree() to reduce chances of use after free.
- Add missing 0x prefix for addresses printed in hexadecimal in 'perf
probe'.
- Suppress massive unsupported target platform errors in the unwind
code.
- Fix return incorrect build_id size in elf_read_build_id().
- Fix 'perf scripts intel-pt-events.py' IPC output for Python 2 .
- Add missing new parameter in kfree_skb tracepoint to the python
scripts using it.
- Add 'perf bench syscall fork' benchmark.
- Add support for printing PERF_MEM_LVLNUM_UNC (Uncached access) in
'perf mem'.
- Fix wrong size expectation for perf test 'Setup struct
perf_event_attr' caused by the patch adding
perf_event_attr::config3.
- Fix some spelling mistakes"
* tag 'perf-tools-for-v6.4-3-2023-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: (365 commits)
Revert "perf build: Make BUILD_BPF_SKEL default, rename to NO_BPF_SKEL"
Revert "perf build: Warn for BPF skeletons if endian mismatches"
perf metrics: Fix SEGV with --for-each-cgroup
perf bpf skels: Stop using vmlinux.h generated from BTF, use subset of used structs + CO-RE
perf stat: Separate bperf from bpf_profiler
perf test record+probe_libc_inet_pton: Fix call chain match on x86_64
perf test record+probe_libc_inet_pton: Fix call chain match on s390
perf tracepoint: Fix memory leak in is_valid_tracepoint()
perf cs-etm: Add fix for coresight trace for any range of CPUs
perf build: Fix unescaped # in perf build-test
perf unwind: Suppress massive unsupported target platform errors
perf script: Add new parameter in kfree_skb tracepoint to the python scripts using it
perf script: Print raw ip instead of binary offset for callchain
perf symbols: Fix return incorrect build_id size in elf_read_build_id()
perf list: Modify the warning message about scandirat(3)
perf list: Fix memory leaks in print_tracepoint_events()
perf lock contention: Rework offset calculation with BPF CO-RE
perf lock contention: Fix struct rq lock access
perf stat: Disable TopdownL1 on hybrid
perf stat: Avoid SEGV on counter->name
...
Pull debugobjects fix from Thomas Gleixner:
"A single fix for debugobjects:
The recent fix to ensure atomicity of lookup and allocation
inadvertently broke the pool refill mechanism, so that debugobject
OOMs now in certain situations. The reason is that the functions which
got updated no longer invoke debug_objecs_init(), which is now the
only place to care about refilling the tracking object pool.
Restore the original behaviour by adding explicit refill opportunities
to those places"
* tag 'core-debugobjects-2023-05-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
debugobject: Ensure pool refill (again)
Pull crypto fixes from Herbert Xu:
- A long-standing bug in crypto_engine
- A buggy but harmless check in the sun8i-ss driver
- A regression in the CRYPTO_USER interface
* tag 'v6.4-p2' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
crypto: api - Fix CRYPTO_USER checks for report function
crypto: engine - fix crypto_queue backlog handling
crypto: sun8i-ss - Fix a test in sun8i_ss_setup_ivs()
Pull cifs fixes from Steve French:
"smb3 client fixes, mostly DFS or reconnect related:
- Two DFS connection sharing fixes
- DFS refresh fix
- Reconnect fix
- Two potential use after free fixes
- Also print prefix patch in mount debug msg
- Two small cleanup fixes"
* tag '6.4-rc-smb3-client-fixes-part2' of git://git.samba.org/sfrench/cifs-2.6:
cifs: Remove unneeded semicolon
cifs: fix sharing of DFS connections
cifs: avoid potential races when handling multiple dfs tcons
cifs: protect access of TCP_Server_Info::{origin,leaf}_fullpath
cifs: fix potential race when tree connecting ipc
cifs: fix potential use-after-free bugs in TCP_Server_Info::hostname
cifs: print smb3_fs_context::source when mounting
cifs: protect session status check in smb2_reconnect()
SMB3.1.1: correct definition for app_instance_id create contexts
Pull clk fixes from Stephen Boyd:
"A couple more patches that would be good to get into -rc1:
- Revert an i.MX patch that's causing video failures because division
math goes sideways
- Fix a clang + W=1 build isue where FIELD_PREP() is taking a 32-bit
variable instead of the usual u64 type
- Fix a Kconfig bug in the StarFive JH7110 clk config that selects a
reset controller when it can't be selected"
* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
clk: starfive: Fix RESET_STARFIVE_JH7110 can't be selected in a specified case
clk: sp7021: Adjust width of _m in HWM_FIELD_PREP()
Revert "clk: imx: composite-8m: Add support to determine_rate"
Pull mailbox updates from Jassi Brar:
- mailbox api: allow direct registration to a channel and convert omap
and pcc to use mbox_bind_client
- omap and hi6220 : use of_property_read_bool
- test: fix double-free and use spinlock header
- rockchip and bcm-pdc: drop of_match_ptr
- mpfs: change config symbol
- mediatek gce: support MT6795
- qcom apcs: consolidate of_device_id and support IPQ9574
* tag 'mailbox-v6.4' of git://git.linaro.org/landing-teams/working/fujitsu/integration:
dt-bindings: mailbox: qcom: add compatible for IPQ9574 SoC
mailbox: qcom-apcs-ipc: do not grow the of_device_id
dt-bindings: mailbox: qcom,apcs-kpss-global: use fallbacks for few variants
dt-bindings: mailbox: mediatek,gce-mailbox: Add support for MT6795
mailbox: mpfs: convert SOC_MICROCHIP_POLARFIRE to ARCH_MICROCHIP_POLARFIRE
mailbox: bcm-pdc: drop of_match_ptr for ID table
mailbox: rockchip: drop of_match_ptr for ID table
mailbox: mailbox-test: Fix potential double-free in mbox_test_message_write()
mailbox: mailbox-test: Explicitly include header for spinlock support
mailbox: Use of_property_read_bool() for boolean properties
mailbox: pcc: Use mbox_bind_client
mailbox: omap: Use mbox_bind_client
mailbox: Allow direct registration to a channel
Pull more io_uring updates from Jens Axboe:
"Nothing major in here, just two different parts:
- A small series from Breno that enables passing the full SQE down
for ->uring_cmd().
This is a prerequisite for enabling full network socket operations.
Queued up a bit late because of some stylistic concerns that got
resolved, would be nice to have this in 6.4-rc1 so the dependent
work will be easier to handle for 6.5.
- Fix for the huge page coalescing, which was a regression introduced
in the 6.3 kernel release (Tobias)"
* tag 'for-6.4/io_uring-2023-05-07' of git://git.kernel.dk/linux:
io_uring: Remove unnecessary BUILD_BUG_ON
io_uring: Pass whole sqe to commands
io_uring: Create a helper to return the SQE size
io_uring/rsrc: check for nonconsecutive pages
This reverts commit a980755beb.
We need to better polish building with BPF skels, so revert back to
making it an experimental feature that has to be explicitely enabled
using BUILD_BPF_SKEL=1.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This reverts commit 51924ae69e.
We need to better polish building with BPF skels, so revert back to
making it an experimental feature that has to be explicitely enabled
using BUILD_BPF_SKEL=1.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull dmapool updates - again - from Andrew Morton:
"Reinstate the dmapool changes which were accidentally removed by a
mishap on the last commit in the previous attempt at the series"
Fixes: 2d55c16c0c ("dmapool: create/destroy cleanup").
[ The whole old series: def8574308ed..2d55c16c0c54 results in an empty
diff because that last commit ended up being just a revert of all that
came everything before it. - Linus ]
* tag 'mm-stable-2023-05-06-10-49' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
dmapool: link blocks across pages
dmapool: don't memset on free twice
dmapool: simplify freeing
dmapool: consolidate page initialization
dmapool: rearrange page alloc failure handling
dmapool: move debug code to own functions
dmapool: speedup DMAPOOL_DEBUG with init_on_alloc
dmapool: cleanup integer types
dmapool: use sysfs_emit() instead of scnprintf()
dmapool: remove checks for dev == NULL
Pull hotfixes from Andrew Morton:
"Five hotfixes.
Three are cc:stable, two pertain to merge window changes"
* tag 'mm-hotfixes-stable-2023-05-06-10-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
afs: fix the afs_dir_get_folio return value
nilfs2: do not write dirty data after degenerating to read-only
mm: do not reclaim private data from pinned page
nilfs2: fix infinite loop in nilfs_mdt_get_block()
mm/mmap/vma_merge: always check invariants
The allocated dmapool pages are never freed for the lifetime of the pool.
There is no need for the two level list+stack lookup for finding a free
block since nothing is ever removed from the list. Just use a simple
stack, reducing time complexity to constant.
The implementation inserts the stack linking elements and the dma handle
of the block within itself when freed. This means the smallest possible
dmapool block is increased to at most 16 bytes to accommodate these
fields, but there are no exisiting users requesting a dma pool smaller
than that anyway.
Removing the list has a significant change in performance. Using the
kernel's micro-benchmarking self test:
Before:
# modprobe dmapool_test
dmapool test: size:16 blocks:8192 time:57282
dmapool test: size:64 blocks:8192 time:172562
dmapool test: size:256 blocks:8192 time:789247
dmapool test: size:1024 blocks:2048 time:371823
dmapool test: size:4096 blocks:1024 time:362237
After:
# modprobe dmapool_test
dmapool test: size:16 blocks:8192 time:24997
dmapool test: size:64 blocks:8192 time:26584
dmapool test: size:256 blocks:8192 time:33542
dmapool test: size:1024 blocks:2048 time:9022
dmapool test: size:4096 blocks:1024 time:6045
The module test allocates quite a few blocks that may not accurately
represent how these pools are used in real life. For a more marco level
benchmark, running fio high-depth + high-batched on nvme, this patch shows
submission and completion latency reduced by ~100usec each, 1% IOPs
improvement, and perf record's time spent in dma_pool_alloc/free were
reduced by half.
[kbusch@kernel.org: push new blocks in ascending order]
Link: https://lkml.kernel.org/r/20230221165400.1595247-1-kbusch@meta.com
Link: https://lkml.kernel.org/r/20230126215125.4069751-12-kbusch@meta.com
Fixes: 2d55c16c0c ("dmapool: create/destroy cleanup")
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
