Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752597AbdIVUBI (ORCPT ); Fri, 22 Sep 2017 16:01:08 -0400 Received: from mga04.intel.com ([192.55.52.120]:26113 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751915AbdIVUBH (ORCPT ); Fri, 22 Sep 2017 16:01:07 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,427,1500966000"; d="scan'208";a="138442685" From: Tom Zanussi To: rostedt@goodmis.org Cc: tglx@linutronix.de, mhiramat@kernel.org, namhyung@kernel.org, vedang.patel@intel.com, bigeasy@linutronix.de, joel.opensrc@gmail.com, joelaf@google.com, mathieu.desnoyers@efficios.com, baohong.liu@intel.com, rajvi.jingar@intel.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Tom Zanussi Subject: [PATCH v3 04/33] ring-buffer: Redefine the unimplemented RINGBUF_TIME_TIME_STAMP Date: Fri, 22 Sep 2017 14:59:44 -0500 Message-Id: <37eccafe797043c80295692825675e28a19f3b12.1506105131.git.tom.zanussi@linux.intel.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10966 Lines: 325 RINGBUF_TYPE_TIME_STAMP is defined but not used, and from what I can gather was reserved for something like an absolute timestamp feature for the ring buffer, if not a complete replacement of the current time_delta scheme. This code redefines RINGBUF_TYPE_TIME_STAMP to implement absolute time stamps. Another way to look at it is that it essentially forces extended time_deltas for all events. The motivation for doing this is to enable time_deltas that aren't dependent on previous events in the ring buffer, making it feasible to use the ring_buffer_event timetamps in a more random-access way, for purposes other than serial event printing. To set/reset this mode, use tracing_set_timestamp_abs() from the previous interface patch. Signed-off-by: Tom Zanussi --- include/linux/ring_buffer.h | 12 ++--- kernel/trace/ring_buffer.c | 105 ++++++++++++++++++++++++++++++++------------ 2 files changed, 83 insertions(+), 34 deletions(-) diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 28e3472..74bc276 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -36,10 +36,12 @@ struct ring_buffer_event { * array[0] = time delta (28 .. 59) * size = 8 bytes * - * @RINGBUF_TYPE_TIME_STAMP: Sync time stamp with external clock - * array[0] = tv_nsec - * array[1..2] = tv_sec - * size = 16 bytes + * @RINGBUF_TYPE_TIME_STAMP: Absolute timestamp + * Same format as TIME_EXTEND except that the + * value is an absolute timestamp, not a delta + * event.time_delta contains bottom 27 bits + * array[0] = top (28 .. 59) bits + * size = 8 bytes * * <= @RINGBUF_TYPE_DATA_TYPE_LEN_MAX: * Data record @@ -56,12 +58,12 @@ enum ring_buffer_type { RINGBUF_TYPE_DATA_TYPE_LEN_MAX = 28, RINGBUF_TYPE_PADDING, RINGBUF_TYPE_TIME_EXTEND, - /* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */ RINGBUF_TYPE_TIME_STAMP, }; unsigned ring_buffer_event_length(struct ring_buffer_event *event); void *ring_buffer_event_data(struct ring_buffer_event *event); +u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event); /* * ring_buffer_discard_commit will remove an event that has not diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 1e5b75a..9dbb459 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -42,6 +42,8 @@ int ring_buffer_print_entry_header(struct trace_seq *s) RINGBUF_TYPE_PADDING); trace_seq_printf(s, "\ttime_extend : type == %d\n", RINGBUF_TYPE_TIME_EXTEND); + trace_seq_printf(s, "\ttime_stamp : type == %d\n", + RINGBUF_TYPE_TIME_STAMP); trace_seq_printf(s, "\tdata max type_len == %d\n", RINGBUF_TYPE_DATA_TYPE_LEN_MAX); @@ -141,12 +143,15 @@ int ring_buffer_print_entry_header(struct trace_seq *s) enum { RB_LEN_TIME_EXTEND = 8, - RB_LEN_TIME_STAMP = 16, + RB_LEN_TIME_STAMP = 8, }; #define skip_time_extend(event) \ ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) +#define extended_time(event) \ + (event->type_len >= RINGBUF_TYPE_TIME_EXTEND) + static inline int rb_null_event(struct ring_buffer_event *event) { return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; @@ -210,7 +215,7 @@ static void rb_event_set_padding(struct ring_buffer_event *event) { unsigned len = 0; - if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { + if (extended_time(event)) { /* time extends include the data event after it */ len = RB_LEN_TIME_EXTEND; event = skip_time_extend(event); @@ -232,7 +237,7 @@ unsigned ring_buffer_event_length(struct ring_buffer_event *event) { unsigned length; - if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) + if (extended_time(event)) event = skip_time_extend(event); length = rb_event_length(event); @@ -249,7 +254,7 @@ unsigned ring_buffer_event_length(struct ring_buffer_event *event) static __always_inline void * rb_event_data(struct ring_buffer_event *event) { - if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) + if (extended_time(event)) event = skip_time_extend(event); BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); /* If length is in len field, then array[0] has the data */ @@ -276,6 +281,27 @@ void *ring_buffer_event_data(struct ring_buffer_event *event) #define TS_MASK ((1ULL << TS_SHIFT) - 1) #define TS_DELTA_TEST (~TS_MASK) +/** + * ring_buffer_event_time_stamp - return the event's extended timestamp + * @event: the event to get the timestamp of + * + * Returns the extended timestamp associated with a data event. + * An extended time_stamp is a 64-bit timestamp represented + * internally in a special way that makes the best use of space + * contained within a ring buffer event. This function decodes + * it and maps it to a straight u64 value. + */ +u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) +{ + u64 ts; + + ts = event->array[0]; + ts <<= TS_SHIFT; + ts += event->time_delta; + + return ts; +} + /* Flag when events were overwritten */ #define RB_MISSED_EVENTS (1 << 31) /* Missed count stored at end */ @@ -2220,13 +2246,16 @@ static void rb_inc_iter(struct ring_buffer_iter *iter) } /* Slow path, do not inline */ -static noinline struct ring_buffer_event * -rb_add_time_stamp(struct ring_buffer_event *event, u64 delta) +static struct noinline ring_buffer_event * +rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs) { - event->type_len = RINGBUF_TYPE_TIME_EXTEND; + if (abs) + event->type_len = RINGBUF_TYPE_TIME_STAMP; + else + event->type_len = RINGBUF_TYPE_TIME_EXTEND; - /* Not the first event on the page? */ - if (rb_event_index(event)) { + /* Not the first event on the page, or not delta? */ + if (abs || rb_event_index(event)) { event->time_delta = delta & TS_MASK; event->array[0] = delta >> TS_SHIFT; } else { @@ -2269,7 +2298,9 @@ static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, * add it to the start of the resevered space. */ if (unlikely(info->add_timestamp)) { - event = rb_add_time_stamp(event, delta); + bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer); + + event = rb_add_time_stamp(event, info->delta, abs); length -= RB_LEN_TIME_EXTEND; delta = 0; } @@ -2457,7 +2488,7 @@ static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer static inline void rb_event_discard(struct ring_buffer_event *event) { - if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) + if (extended_time(event)) event = skip_time_extend(event); /* array[0] holds the actual length for the discarded event */ @@ -2488,6 +2519,10 @@ static inline void rb_event_discard(struct ring_buffer_event *event) { u64 delta; + /* In TIME_STAMP mode, write_stamp is unused, nothing to do */ + if (event->type_len == RINGBUF_TYPE_TIME_STAMP) + return; + /* * The event first in the commit queue updates the * time stamp. @@ -2501,9 +2536,7 @@ static inline void rb_event_discard(struct ring_buffer_event *event) cpu_buffer->write_stamp = cpu_buffer->commit_page->page->time_stamp; else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { - delta = event->array[0]; - delta <<= TS_SHIFT; - delta += event->time_delta; + delta = ring_buffer_event_time_stamp(event); cpu_buffer->write_stamp += delta; } else cpu_buffer->write_stamp += event->time_delta; @@ -2657,7 +2690,7 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer, * If this is the first commit on the page, then it has the same * timestamp as the page itself. */ - if (!tail) + if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer)) info->delta = 0; /* See if we shot pass the end of this buffer page */ @@ -2735,8 +2768,11 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer, /* make sure this diff is calculated here */ barrier(); - /* Did the write stamp get updated already? */ - if (likely(info.ts >= cpu_buffer->write_stamp)) { + if (ring_buffer_time_stamp_abs(buffer)) { + info.delta = info.ts; + rb_handle_timestamp(cpu_buffer, &info); + } else /* Did the write stamp get updated already? */ + if (likely(info.ts >= cpu_buffer->write_stamp)) { info.delta = diff; if (unlikely(test_time_stamp(info.delta))) rb_handle_timestamp(cpu_buffer, &info); @@ -3418,14 +3454,12 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter) return; case RINGBUF_TYPE_TIME_EXTEND: - delta = event->array[0]; - delta <<= TS_SHIFT; - delta += event->time_delta; + delta = ring_buffer_event_time_stamp(event); cpu_buffer->read_stamp += delta; return; case RINGBUF_TYPE_TIME_STAMP: - /* FIXME: not implemented */ + /* In TIME_STAMP mode, write_stamp is unused, nothing to do */ return; case RINGBUF_TYPE_DATA: @@ -3449,14 +3483,12 @@ int ring_buffer_iter_empty(struct ring_buffer_iter *iter) return; case RINGBUF_TYPE_TIME_EXTEND: - delta = event->array[0]; - delta <<= TS_SHIFT; - delta += event->time_delta; + delta = ring_buffer_event_time_stamp(event); iter->read_stamp += delta; return; case RINGBUF_TYPE_TIME_STAMP: - /* FIXME: not implemented */ + /* In TIME_STAMP mode, write_stamp is unused, nothing to do */ return; case RINGBUF_TYPE_DATA: @@ -3680,6 +3712,8 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) struct buffer_page *reader; int nr_loops = 0; + if (ts) + *ts = 0; again: /* * We repeat when a time extend is encountered. @@ -3716,12 +3750,17 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) goto again; case RINGBUF_TYPE_TIME_STAMP: - /* FIXME: not implemented */ + if (ts) { + *ts = ring_buffer_event_time_stamp(event); + ring_buffer_normalize_time_stamp(cpu_buffer->buffer, + cpu_buffer->cpu, ts); + } + /* Internal data, OK to advance */ rb_advance_reader(cpu_buffer); goto again; case RINGBUF_TYPE_DATA: - if (ts) { + if (ts && !(*ts)) { *ts = cpu_buffer->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu, ts); @@ -3746,6 +3785,9 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) struct ring_buffer_event *event; int nr_loops = 0; + if (ts) + *ts = 0; + cpu_buffer = iter->cpu_buffer; buffer = cpu_buffer->buffer; @@ -3798,12 +3840,17 @@ static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer) goto again; case RINGBUF_TYPE_TIME_STAMP: - /* FIXME: not implemented */ + if (ts) { + *ts = ring_buffer_event_time_stamp(event); + ring_buffer_normalize_time_stamp(cpu_buffer->buffer, + cpu_buffer->cpu, ts); + } + /* Internal data, OK to advance */ rb_advance_iter(iter); goto again; case RINGBUF_TYPE_DATA: - if (ts) { + if (ts && !(*ts)) { *ts = iter->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(buffer, cpu_buffer->cpu, ts); -- 1.9.3