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Subject[PATCH 1/2] tracing/core: make the per cpu trace files in per cpu directories
Impact: scale per cpu tracing

The per cpu trace files are all in a single directory: /debug/tracing/per_cpu.
In case of a large number of cpu, the content of this directory becomes messy
so we create now one directory per cpu inside /debug/tracing/per_cpu which contain
each their own trace_pipe and trace files.

Ie:

nobody@nowhere:/debug/tracing$ ls -R per_cpu
per_cpu:
cpu0 cpu1

per_cpu/cpu0:
trace trace_pipe

per_cpu/cpu1:
trace trace_pipe

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
---
kernel/trace/trace.c | 25 ++++++++++++++-----------
1 files changed, 14 insertions(+), 11 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b7eeecc..b1f7105 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3061,28 +3061,31 @@ struct dentry *tracing_dentry_percpu(void)
static void tracing_init_debugfs_percpu(long cpu)
{
struct dentry *d_percpu = tracing_dentry_percpu();
- struct dentry *entry;
- /* strlen(trace_pipe) + MAX(log10(cpu)) + '\0' */
- char filename[17];
+ struct dentry *entry, *d_cpu;
+ /* strlen(cpu) + MAX(log10(cpu)) + '\0' */
+ char cpu_dir[7];

if (cpu > 999 || cpu < 0)
return;

- /* per cpu trace_pipe */
- sprintf(filename, "trace_pipe%ld", cpu);
+ sprintf(cpu_dir, "cpu%ld", cpu);
+ d_cpu = debugfs_create_dir(cpu_dir, d_percpu);
+ if (!d_cpu) {
+ pr_warning("Could not create debugfs '%s' entry\n", cpu_dir);
+ return;
+ }

- entry = debugfs_create_file(filename, 0444, d_percpu,
+ /* per cpu trace_pipe */
+ entry = debugfs_create_file("trace_pipe", 0444, d_cpu,
(void *) cpu, &tracing_pipe_fops);
if (!entry)
- pr_warning("Could not create debugfs '%s' entry\n", filename);
+ pr_warning("Could not create debugfs 'trace_pipe' entry\n");

/* per cpu trace */
- sprintf(filename, "trace%ld", cpu);
-
- entry = debugfs_create_file(filename, 0444, d_percpu,
+ entry = debugfs_create_file("trace", 0444, d_cpu,
(void *) cpu, &tracing_fops);
if (!entry)
- pr_warning("Could not create debugfs '%s' entry\n", filename);
+ pr_warning("Could not create debugfs 'trace' entry\n");

}

--
1.6.1



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