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perf: split perf_trace_buf_prepare into alloc and update parts

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split allows to move expensive update of 'struct trace_entry' to later phase.
Repurpose unused 1st argument of perf_tp_event() to indicate event type.

While splitting use temp variable 'rctx' instead of '*rctx' to avoid
unnecessary loads done by the compiler due to -fno-strict-aliasing

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov
2016-04-06 18:43:24 -07:00
committed by David S. Miller
parent e93735be6a
commit 1e1dcd93b4
8 changed files with 49 additions and 42 deletions
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39
kernel/trace/trace_event_perf.c
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@@ -260,42 +260,43 @@ void perf_trace_del(struct perf_event *p_event, int flags)
tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event);
}
void *perf_trace_buf_prepare(int size, unsigned short type,
struct pt_regs **regs, int *rctxp)
void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)
{
struct trace_entry *entry;
unsigned long flags;
char *raw_data;
int pc;
int rctx;
BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));
if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
"perf buffer not large enough"))
"perf buffer not large enough"))
return NULL;
pc = preempt_count();
*rctxp = perf_swevent_get_recursion_context();
if (*rctxp < 0)
*rctxp = rctx = perf_swevent_get_recursion_context();
if (rctx < 0)
return NULL;
if (regs)
*regs = this_cpu_ptr(&__perf_regs[*rctxp]);
raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);
*regs = this_cpu_ptr(&__perf_regs[rctx]);
raw_data = this_cpu_ptr(perf_trace_buf[rctx]);
/* zero the dead bytes from align to not leak stack to user */
memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
return raw_data;
}
EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
NOKPROBE_SYMBOL(perf_trace_buf_alloc);
void perf_trace_buf_update(void *record, u16 type)
{
struct trace_entry *entry = record;
int pc = preempt_count();
unsigned long flags;
entry = (struct trace_entry *)raw_data;
local_save_flags(flags);
tracing_generic_entry_update(entry, flags, pc);
entry->type = type;
return raw_data;
}
EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);
NOKPROBE_SYMBOL(perf_trace_buf_prepare);
NOKPROBE_SYMBOL(perf_trace_buf_update);
#ifdef CONFIG_FUNCTION_TRACER
static void
@@ -319,13 +320,13 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
memset(&regs, 0, sizeof(regs));
perf_fetch_caller_regs(&regs);
entry = perf_trace_buf_prepare(ENTRY_SIZE, TRACE_FN, NULL, &rctx);
entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);
if (!entry)
return;
entry->ip = ip;
entry->parent_ip = parent_ip;
perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,
1, &regs, head, NULL);
#undef ENTRY_SIZE