Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755829Ab0LHVr1 (ORCPT ); Wed, 8 Dec 2010 16:47:27 -0500 Received: from smtp-out.google.com ([216.239.44.51]:29867 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752512Ab0LHVrY (ORCPT ); Wed, 8 Dec 2010 16:47:24 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=R/HVsIX1pSVYIR6A4CEdl87LXI57zLJp4QI/VzmEJyotK0EMxRTSG40r7lTC25wML GZL9YYKnI2RYuBcdsInsA== From: David Sharp To: rostedt@goodmis.org Cc: linux-kernel@vger.kernel.org, mrubin@google.com, jiayingz@google.com, David Sharp Subject: [PATCH] tracing: Add an 'overwrite' trace_option. Date: Wed, 8 Dec 2010 13:46:47 -0800 Message-Id: <1291844807-15481-1-git-send-email-dhsharp@google.com> X-Mailer: git-send-email 1.7.3.1 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5658 Lines: 161 Add an "overwrite" trace_option for ftrace to control whether the buffer should be overwritten on overflow or not. The default remains to overwrite old events when the buffer is full. This patch adds the option to instead discard newest events when the buffer is full. This is useful to get a snapshot of traces just after enabling traces. Dropping the current event is also a simpler code path. --- Documentation/trace/ftrace.txt | 5 +++++ include/linux/ring_buffer.h | 2 ++ kernel/trace/ring_buffer.c | 11 +++++++++++ kernel/trace/trace.c | 17 +++++++++++------ kernel/trace/trace.h | 1 + 5 files changed, 30 insertions(+), 6 deletions(-) diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index 557c1ed..2842ea7 100644 --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -491,6 +491,11 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6] latencies, as described in "Latency trace format". + overwrite - This controls what happens when the trace buffer is + full. If "1" (default), the oldest events are + discarded and overwritten. If "0", then the newest + events are discarded. + sched_switch ------------ diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 8d3a248..ab38ac8 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -100,6 +100,8 @@ void ring_buffer_free(struct ring_buffer *buffer); int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size); +void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val); + struct ring_buffer_event *ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length); int ring_buffer_unlock_commit(struct ring_buffer *buffer, diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 9ed509a..3207147 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1429,6 +1429,17 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) } EXPORT_SYMBOL_GPL(ring_buffer_resize); +void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) +{ + mutex_lock(&buffer->mutex); + if (val) + buffer->flags |= RB_FL_OVERWRITE; + else + buffer->flags &= ~RB_FL_OVERWRITE; + mutex_unlock(&buffer->mutex); +} +EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); + static inline void * __rb_data_page_index(struct buffer_data_page *bpage, unsigned index) { diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index c380612..6f7494c 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -41,8 +41,6 @@ #include "trace.h" #include "trace_output.h" -#define TRACE_BUFFER_FLAGS (RB_FL_OVERWRITE) - /* * On boot up, the ring buffer is set to the minimum size, so that * we do not waste memory on systems that are not using tracing. @@ -340,7 +338,7 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait); /* trace_flags holds trace_options default values */ unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK | TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO | TRACE_ITER_SLEEP_TIME | - TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD; + TRACE_ITER_GRAPH_TIME | TRACE_ITER_RECORD_CMD | TRACE_ITER_OVERWRITE; static int trace_stop_count; static DEFINE_SPINLOCK(tracing_start_lock); @@ -425,6 +423,7 @@ static const char *trace_options[] = { "sleep-time", "graph-time", "record-cmd", + "overwrite", NULL }; @@ -2523,6 +2522,9 @@ static void set_tracer_flags(unsigned int mask, int enabled) if (mask == TRACE_ITER_RECORD_CMD) trace_event_enable_cmd_record(enabled); + + if (mask == TRACE_ITER_OVERWRITE) + ring_buffer_change_overwrite(global_trace.buffer, enabled); } static ssize_t @@ -4545,9 +4547,11 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) __init static int tracer_alloc_buffers(void) { int ring_buf_size; + enum ring_buffer_flags rb_flags; int i; int ret = -ENOMEM; + if (!alloc_cpumask_var(&tracing_buffer_mask, GFP_KERNEL)) goto out; @@ -4560,12 +4564,13 @@ __init static int tracer_alloc_buffers(void) else ring_buf_size = 1; + rb_flags = trace_flags & TRACE_ITER_OVERWRITE ? RB_FL_OVERWRITE : 0; + cpumask_copy(tracing_buffer_mask, cpu_possible_mask); cpumask_copy(tracing_cpumask, cpu_all_mask); /* TODO: make the number of buffers hot pluggable with CPUS */ - global_trace.buffer = ring_buffer_alloc(ring_buf_size, - TRACE_BUFFER_FLAGS); + global_trace.buffer = ring_buffer_alloc(ring_buf_size, rb_flags); if (!global_trace.buffer) { printk(KERN_ERR "tracer: failed to allocate ring buffer!\n"); WARN_ON(1); @@ -4575,7 +4580,7 @@ __init static int tracer_alloc_buffers(void) #ifdef CONFIG_TRACER_MAX_TRACE - max_tr.buffer = ring_buffer_alloc(1, TRACE_BUFFER_FLAGS); + max_tr.buffer = ring_buffer_alloc(1, rb_flags); if (!max_tr.buffer) { printk(KERN_ERR "tracer: failed to allocate max ring buffer!\n"); WARN_ON(1); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 9021f8c..9cd025a 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -606,6 +606,7 @@ enum trace_iterator_flags { TRACE_ITER_SLEEP_TIME = 0x40000, TRACE_ITER_GRAPH_TIME = 0x80000, TRACE_ITER_RECORD_CMD = 0x100000, + TRACE_ITER_OVERWRITE = 0x200000, }; /* -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/