Messages in this thread | | | Date | Mon, 17 Jun 2013 13:33:40 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH 1/3] tracing/kprobes: Avoid perf_trace_buf_*() if ->perf_events is empty |
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(2013/06/17 2:21), Oleg Nesterov wrote: > perf_trace_buf_prepare() + perf_trace_buf_submit() make no sense > if this task/CPU has no active counters. Change kprobe_perf_func() > and kretprobe_perf_func() to check call->perf_events beforehand > and return if this list is empty. > > For example, "perf record -e some_probe -p1". Only /sbin/init will > report, all other threads which hit the same probe will do > perf_trace_buf_prepare/perf_trace_buf_submit just to realize that > nobody wants perf_swevent_event(). > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Looks good :) Thank you!
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> --- > kernel/trace/trace_kprobe.c | 12 ++++++++---- > 1 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 9f46e98..c0af476 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1157,6 +1157,10 @@ kprobe_perf_func(struct trace_probe *tp, struct pt_regs *regs) > int size, __size, dsize; > int rctx; > > + head = this_cpu_ptr(call->perf_events); > + if (hlist_empty(head)) > + return; > + > dsize = __get_data_size(tp, regs); > __size = sizeof(*entry) + tp->size + dsize; > size = ALIGN(__size + sizeof(u32), sizeof(u64)); > @@ -1172,8 +1176,6 @@ kprobe_perf_func(struct trace_probe *tp, struct pt_regs *regs) > entry->ip = (unsigned long)tp->rp.kp.addr; > memset(&entry[1], 0, dsize); > store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize); > - > - head = this_cpu_ptr(call->perf_events); > perf_trace_buf_submit(entry, size, rctx, > entry->ip, 1, regs, head, NULL); > } > @@ -1189,6 +1191,10 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri, > int size, __size, dsize; > int rctx; > > + head = this_cpu_ptr(call->perf_events); > + if (hlist_empty(head)) > + return; > + > dsize = __get_data_size(tp, regs); > __size = sizeof(*entry) + tp->size + dsize; > size = ALIGN(__size + sizeof(u32), sizeof(u64)); > @@ -1204,8 +1210,6 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri, > entry->func = (unsigned long)tp->rp.kp.addr; > entry->ret_ip = (unsigned long)ri->ret_addr; > store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize); > - > - head = this_cpu_ptr(call->perf_events); > perf_trace_buf_submit(entry, size, rctx, > entry->ret_ip, 1, regs, head, NULL); > } >
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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