perf core: Separate accounting of contexts and real addresses in a stack trace

The perf_sample->ip_callchain->nr value includes all the entries in the
ip_callchain->ip[] array, real addresses and PERF_CONTEXT_{KERNEL,USER,etc},
while what the user expects is that what is in the kernel.perf_event_max_stack
sysctl or in the upcoming per event perf_event_attr.sample_max_stack knob be
honoured in terms of IP addresses in the stack trace.

So allocate a bunch of extra entries for contexts, and do the accounting
via perf_callchain_entry_ctx struct members.

A new sysctl, kernel.perf_event_max_contexts_per_stack is also
introduced for investigating possible bugs in the callchain
implementation by some arch.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/n/tip-3b4wnqk340c4sg4gwkfdi9yk@git.kernel.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 3e4de4ec
......@@ -61,6 +61,7 @@ show up in /proc/sys/kernel:
- perf_cpu_time_max_percent
- perf_event_paranoid
- perf_event_max_stack
- perf_event_max_contexts_per_stack
- pid_max
- powersave-nap [ PPC only ]
- printk
......@@ -668,6 +669,19 @@ The default value is 127.
==============================================================
perf_event_max_contexts_per_stack:
Controls maximum number of stack frame context entries for
(attr.sample_type & PERF_SAMPLE_CALLCHAIN) configured events, for
instance, when using 'perf record -g' or 'perf trace --call-graph fp'.
This can only be done when no events are in use that have callchains
enabled, otherwise writing to this file will return -EBUSY.
The default value is 8.
==============================================================
pid_max:
PID allocation wrap value. When the kernel's next PID value
......
......@@ -65,6 +65,8 @@ struct perf_callchain_entry_ctx {
struct perf_callchain_entry *entry;
u32 max_stack;
u32 nr;
short contexts;
bool contexts_maxed;
};
struct perf_raw_record {
......@@ -1078,12 +1080,24 @@ extern int get_callchain_buffers(void);
extern void put_callchain_buffers(void);
extern int sysctl_perf_event_max_stack;
extern int sysctl_perf_event_max_contexts_per_stack;
#define perf_callchain_store_context(ctx, context) perf_callchain_store(ctx, context)
static inline int perf_callchain_store_context(struct perf_callchain_entry_ctx *ctx, u64 ip)
{
if (ctx->contexts < sysctl_perf_event_max_contexts_per_stack) {
struct perf_callchain_entry *entry = ctx->entry;
entry->ip[entry->nr++] = ip;
++ctx->contexts;
return 0;
} else {
ctx->contexts_maxed = true;
return -1; /* no more room, stop walking the stack */
}
}
static inline int perf_callchain_store(struct perf_callchain_entry_ctx *ctx, u64 ip)
{
if (ctx->nr < ctx->max_stack) {
if (ctx->nr < ctx->max_stack && !ctx->contexts_maxed) {
struct perf_callchain_entry *entry = ctx->entry;
entry->ip[entry->nr++] = ip;
++ctx->nr;
......
......@@ -862,6 +862,7 @@ enum perf_event_type {
};
#define PERF_MAX_STACK_DEPTH 127
#define PERF_MAX_CONTEXTS_PER_STACK 8
enum perf_callchain_context {
PERF_CONTEXT_HV = (__u64)-32,
......
......@@ -19,11 +19,13 @@ struct callchain_cpus_entries {
};
int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
static inline size_t perf_callchain_entry__sizeof(void)
{
return (sizeof(struct perf_callchain_entry) +
sizeof(__u64) * sysctl_perf_event_max_stack);
sizeof(__u64) * (sysctl_perf_event_max_stack +
sysctl_perf_event_max_contexts_per_stack));
}
static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
......@@ -197,6 +199,8 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
ctx.entry = entry;
ctx.max_stack = max_stack;
ctx.nr = entry->nr = init_nr;
ctx.contexts = 0;
ctx.contexts_maxed = false;
if (kernel && !user_mode(regs)) {
if (add_mark)
......@@ -228,6 +232,10 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
return entry;
}
/*
* Used for sysctl_perf_event_max_stack and
* sysctl_perf_event_max_contexts_per_stack.
*/
int perf_event_max_stack_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
......
......@@ -1156,6 +1156,15 @@ static struct ctl_table kern_table[] = {
.extra1 = &zero,
.extra2 = &six_hundred_forty_kb,
},
{
.procname = "perf_event_max_contexts_per_stack",
.data = &sysctl_perf_event_max_contexts_per_stack,
.maxlen = sizeof(sysctl_perf_event_max_contexts_per_stack),
.mode = 0644,
.proc_handler = perf_event_max_stack_handler,
.extra1 = &zero,
.extra2 = &one_thousand,
},
#endif
#ifdef CONFIG_KMEMCHECK
{
......
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