diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2020-06-25 15:34:03 +1000 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-06-30 17:18:56 -0400 |
| commit | b23d7a5f4a07af02343cdd28fe1f7488bac3afda (patch) | |
| tree | c775987b3e84915ec4c22a410f65c8c145ee70ce /kernel/trace/trace.c | |
| parent | 10464b4aa605ef93c937452f442e74cc0a4a6ceb (diff) | |
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>
Diffstat (limited to 'kernel/trace/trace.c')
| -rw-r--r-- | kernel/trace/trace.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 64c5b8146cca..4aab712f9567 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2003,7 +2003,6 @@ static void tracing_reset_cpu(struct array_buffer *buf, int cpu) void tracing_reset_online_cpus(struct array_buffer *buf) { struct trace_buffer *buffer = buf->buffer; - int cpu; if (!buffer) return; @@ -2015,8 +2014,7 @@ void tracing_reset_online_cpus(struct array_buffer *buf) buf->time_start = buffer_ftrace_now(buf, buf->cpu); - for_each_online_cpu(cpu) - ring_buffer_reset_cpu(buffer, cpu); + ring_buffer_reset_online_cpus(buffer); ring_buffer_record_enable(buffer); } |