linux/kernel/trace
Nicholas Piggin b23d7a5f4a ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU
On a 144 thread system, `perf ftrace` takes about 20 seconds to start
up, due to calling synchronize_rcu() for each CPU.

  cat /proc/108560/stack
    0xc0003e7eb336f470
    __switch_to+0x2e0/0x480
    __wait_rcu_gp+0x20c/0x220
    synchronize_rcu+0x9c/0xc0
    ring_buffer_reset_cpu+0x88/0x2e0
    tracing_reset_online_cpus+0x84/0xe0
    tracing_open+0x1d4/0x1f0

On a system with 10x more threads, it starts to become an annoyance.

Batch these up so we disable all the per-cpu buffers first, then
synchronize_rcu() once, then reset each of the buffers. This brings
the time down to about 0.5s.

Link: https://lkml.kernel.org/r/20200625053403.2386972-1-npiggin@gmail.com

Tested-by: Anton Blanchard <anton@ozlabs.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2020-06-30 17:18:56 -04:00
..
blktrace.c blktrace: Avoid sparse warnings when assigning q->blk_trace 2020-06-17 09:07:11 -06:00
bpf_trace.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-25 18:27:40 -07:00
fgraph.c tracing: Define MCOUNT_INSN_SIZE when not defined without direct calls 2020-01-02 21:56:44 -05:00
ftrace_internal.h x86/ftrace: Have ftrace trampolines turn read-only at the end of system boot up 2020-05-12 18:24:34 -04:00
ftrace.c x86/ftrace: Only have the builtin ftrace_regs_caller call direct hooks 2020-06-29 11:42:47 -04:00
Kconfig Tracing updates for 5.8: 2020-06-09 10:06:18 -07:00
kprobe_event_gen_test.c tracing: Add kprobe event command generation test module 2020-01-30 09:46:28 -05:00
Makefile Rebase locking/kcsan to locking/urgent 2020-06-11 20:02:46 +02:00
power-traces.c
preemptirq_delay_test.c tracing: Wait for preempt irq delay thread to execute 2020-05-11 17:00:34 -04:00
ring_buffer_benchmark.c tracing: Make struct ring_buffer less ambiguous 2020-01-13 13:19:38 -05:00
ring_buffer.c ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU 2020-06-30 17:18:56 -04:00
rpm-traces.c
synth_event_gen_test.c tracing: Have synthetic event test use raw_smp_processor_id() 2020-02-20 17:43:41 -05:00
trace_benchmark.c trace: Use pr_warn instead of pr_warning 2019-10-18 15:01:57 +02:00
trace_benchmark.h
trace_boot.c tracing/boottime: Fix kprobe multiple events 2020-06-23 21:51:50 -04:00
trace_branch.c tracing: Make struct ring_buffer less ambiguous 2020-01-13 13:19:38 -05:00
trace_clock.c
trace_dynevent.c tracing: Use seq_buf for building dynevent_cmd string 2020-02-01 13:10:15 -05:00
trace_dynevent.h tracing: Remove check_arg() callbacks from dynevent args 2020-02-01 13:09:23 -05:00
trace_entries.h tracing: Make ftrace packed events have align of 1 2020-06-16 21:21:02 -04:00
trace_event_perf.c Merge branch 'perf/urgent' into perf/core, to pick up fixes 2019-10-28 12:38:26 +01:00
trace_events_filter_test.h
trace_events_filter.c tracing: Avoid memory leak in process_system_preds() 2019-12-19 18:24:17 -05:00
trace_events_hist.c tracing: Move synthetic events to a separate file 2020-06-01 08:23:22 -04:00
trace_events_inject.c tracing: Initialize val to zero in parse_entry of inject code 2020-01-02 19:04:57 -05:00
trace_events_synth.c tracing: Move synthetic events to a separate file 2020-06-01 08:23:22 -04:00
trace_events_trigger.c tracing: Fix event trigger to accept redundant spaces 2020-06-23 21:51:40 -04:00
trace_events.c tracing: Add hist_debug trace event files for histogram debugging 2020-06-01 08:22:30 -04:00
trace_export.c tracing: Make ftrace packed events have align of 1 2020-06-16 21:21:02 -04:00
trace_functions_graph.c ring-buffer: Rename ring_buffer_read() to read_buffer_iter_advance() 2020-03-19 19:11:19 -04:00
trace_functions.c trace: Fix typo in allocate_ftrace_ops()'s comment 2020-06-16 21:21:02 -04:00
trace_hwlat.c tracing: Have hwlat ts be first instance and record count of instances 2020-03-03 17:33:43 -05:00
trace_irqsoff.c tracing: Rename trace_buffer to array_buffer 2020-01-13 13:19:38 -05:00
trace_kdb.c tracing: Rename trace_buffer to array_buffer 2020-01-13 13:19:38 -05:00
trace_kprobe_selftest.c
trace_kprobe_selftest.h
trace_kprobe.c maccess: rename probe_user_{read,write} to copy_{from,to}_user_nofault 2020-06-17 10:57:41 -07:00
trace_mmiotrace.c tracing: Make struct ring_buffer less ambiguous 2020-01-13 13:19:38 -05:00
trace_nop.c
trace_output.c mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
trace_output.h
trace_preemptirq.c x86/entry: Rename trace_hardirqs_off_prepare() 2020-06-11 15:15:24 +02:00
trace_printk.c tracing: Add locked_down checks to the open calls of files created for tracefs 2019-10-12 20:48:06 -04:00
trace_probe_tmpl.h tracing/probe: Support user-space dereference 2019-05-25 23:04:42 -04:00
trace_probe.c tracing/probe: Fix memleak in fetch_op_data operations 2020-06-16 21:21:02 -04:00
trace_probe.h tracing/probe: Replace zero-length array with flexible-array 2020-06-15 23:08:32 -05:00
trace_sched_switch.c tracing: Fix sched switch start/stop refcount racy updates 2020-01-30 09:46:10 -05:00
trace_sched_wakeup.c tracing: Make struct ring_buffer less ambiguous 2020-01-13 13:19:38 -05:00
trace_selftest_dynamic.c
trace_selftest.c tracing: Rename trace_buffer to array_buffer 2020-01-13 13:19:38 -05:00
trace_seq.c tracing: Remove unused TRACE_SEQ_BUF_USED 2020-01-21 18:39:54 -05:00
trace_stack.c trace: fix an incorrect __user annotation on stack_trace_sysctl 2020-06-08 10:13:56 -04:00
trace_stat.c tracing: Fix tracing_stat return values in error handling paths 2020-01-24 18:06:48 -05:00
trace_stat.h tracing: Use generic type for comparator function 2019-11-14 13:15:11 -05:00
trace_synth.h tracing: Move synthetic events to a separate file 2020-06-01 08:23:22 -04:00
trace_syscalls.c Tracing updates: 2020-02-06 07:12:11 +00:00
trace_uprobe.c tracing/probe: Fix bpf_task_fd_query() for kprobes and uprobes 2020-06-09 11:10:12 -07:00
trace.c ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU 2020-06-30 17:18:56 -04:00
trace.h tracing: Move pipe reference to trace array instead of current_tracer 2020-06-30 14:29:33 -04:00
tracing_map.c tracing: Convert local functions in tracing_map.c to static 2020-04-22 22:07:26 -04:00
tracing_map.h