From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: [PATCH 03/18] ring-buffer: remove unnecessary cpu_relax
Date: Fri, 04 Sep 2009 19:55:30 -0400 [thread overview]
Message-ID: <20090905000121.298060241@goodmis.org> (raw)
In-Reply-To: 20090904235527.520961911@goodmis.org
[-- Attachment #1: 0003-ring-buffer-remove-unnecessary-cpu_relax.patch --]
[-- Type: text/plain, Size: 1890 bytes --]
From: Steven Rostedt <srostedt@redhat.com>
The loops in the ring buffer that use cpu_relax are not dependent on
other CPUs. They simply came across some padding in the ring buffer and
are skipping over them. It is a normal loop and does not require a
cpu_relax.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/ring_buffer.c | 16 ++++------------
1 files changed, 4 insertions(+), 12 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2878bd4..a05541a 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3132,10 +3132,8 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);
- if (event && event->type_len == RINGBUF_TYPE_PADDING) {
- cpu_relax();
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
- }
return event;
}
@@ -3160,10 +3158,8 @@ ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
event = rb_iter_peek(iter, ts);
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
- if (event && event->type_len == RINGBUF_TYPE_PADDING) {
- cpu_relax();
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
- }
return event;
}
@@ -3209,10 +3205,8 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
out:
preempt_enable();
- if (event && event->type_len == RINGBUF_TYPE_PADDING) {
- cpu_relax();
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
- }
return event;
}
@@ -3302,10 +3296,8 @@ ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
out:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
- if (event && event->type_len == RINGBUF_TYPE_PADDING) {
- cpu_relax();
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
- }
return event;
}
--
1.6.3.3
--
next prev parent reply other threads:[~2009-09-05 0:03 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-04 23:55 [PATCH 00/18] tracing/ring-buffer: fixes for latency tracer [2.6.32] Steven Rostedt
2009-09-04 23:55 ` [PATCH 01/18] ring-buffer: do not reset while in a commit Steven Rostedt
2009-09-04 23:55 ` [PATCH 02/18] ring-buffer: do not swap buffers during " Steven Rostedt
2009-09-04 23:55 ` Steven Rostedt [this message]
2009-09-04 23:55 ` [PATCH 04/18] ring-buffer: fix ring_buffer_read crossing pages Steven Rostedt
2009-09-04 23:55 ` [PATCH 05/18] ring-buffer: remove ring_buffer_event_discard Steven Rostedt
2009-09-04 23:55 ` [PATCH 06/18] ring-buffer: do not count discarded events Steven Rostedt
2009-09-04 23:55 ` [PATCH 07/18] ring-buffer: disable all cpu buffers when one finds a problem Steven Rostedt
2009-09-04 23:55 ` [PATCH 08/18] tracing: print out start and stop in latency traces Steven Rostedt
2009-09-04 23:55 ` [PATCH 09/18] tracing: disable update max tracer while reading trace Steven Rostedt
2009-09-04 23:55 ` [PATCH 10/18] tracing: disable buffers and synchronize_sched before resetting Steven Rostedt
2009-09-04 23:55 ` [PATCH 11/18] tracing: remove users of tracing_reset Steven Rostedt
2009-09-04 23:55 ` [PATCH 12/18] tracing: use timestamp to determine start of latency traces Steven Rostedt
2009-09-04 23:55 ` [PATCH 13/18] tracing: make tracing_reset safe for external use Steven Rostedt
2009-09-04 23:55 ` [PATCH 14/18] tracing: pass around ring buffer instead of tracer Steven Rostedt
2009-09-04 23:55 ` [PATCH 15/18] tracing: add trace_array_printk for internal tracers to use Steven Rostedt
2009-09-04 23:55 ` [PATCH 16/18] tracing: report error in trace if we fail to swap latency buffer Steven Rostedt
2009-09-04 23:55 ` [PATCH 17/18] ring-buffer: check for swapped buffers in start of committing Steven Rostedt
2009-09-04 23:55 ` [PATCH 18/18] ring-buffer: only enable ring_buffer_swap_cpu when needed Steven Rostedt
2009-09-05 15:06 ` [PATCH 00/18] tracing/ring-buffer: fixes for latency tracer [2.6.32] Arnaldo Carvalho de Melo
2009-09-07 10:20 ` Jan Blunck
2009-09-07 10:20 ` Jan Blunck
2009-09-07 10:28 ` Frederic Weisbecker
2009-09-07 10:41 ` Jan Blunck
2009-09-07 11:22 ` Frederic Weisbecker
2009-09-08 14:42 ` Jan Blunck
2009-09-08 14:42 ` Jan Blunck
2009-09-08 15:39 ` Steven Rostedt
2009-09-08 15:39 ` Steven Rostedt
2009-09-06 4:19 ` Ingo Molnar
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