Messages in this thread |  | | | From | David Sharp <> | | Date | Wed, 8 Dec 2010 12:15:51 -0800 | | Subject | Re: [PATCH 01/15] tracing: Add a 'buffer_overwrite' debugfs file |
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On Fri, Dec 3, 2010 at 5:57 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > On Fri, 2010-12-03 at 16:13 -0800, David Sharp wrote: >> From: Jiaying Zhang <jiayingz@google.com> >> >> Add a "buffer_overwrite" debugfs file for ftrace to control whether the buffer > > Instead of adding a new file, make this another "trace_option".
To do this, I had to add a special case to set_tracer_flags() to call ring_buffer_change_overwrite. It also means adding something not iterator-related to trace_iterator_flags. Although, maybe it's just the name of the enum and value prefix that should change.
I'll send the new patch to you separately today.
> > Thanks, > > -- Steve > > >> 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. >> >> Signed-off-by: David Sharp <dhsharp@google.com> >> --- >> Documentation/trace/ftrace.txt | 6 ++++ >> include/linux/ring_buffer.h | 2 + >> kernel/trace/ring_buffer.c | 11 +++++++ >> kernel/trace/trace.c | 59 +++++++++++++++++++++++++++++++++++++--- >> 4 files changed, 74 insertions(+), 4 deletions(-) >> >> diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt >> index 557c1ed..9237da3 100644 >> --- a/Documentation/trace/ftrace.txt >> +++ b/Documentation/trace/ftrace.txt >> @@ -138,6 +138,12 @@ of ftrace. Here is a list of some of the key files: >> This can only be updated when the current_tracer >> is set to "nop". >> >> + buffer_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. >> + >> tracing_cpumask: >> >> This is a mask that lets the user only trace >> 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..ed5c14f 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. >> @@ -241,6 +239,9 @@ int tracing_is_enabled(void) >> >> static unsigned long trace_buf_size = TRACE_BUF_SIZE_DEFAULT; >> >> +/* whether the trace buffer should be overwritten on overflow or not. */ >> +static enum ring_buffer_flags trace_buffer_flags = RB_FL_OVERWRITE; >> + >> /* trace_types holds a link list of available tracers. */ >> static struct tracer *trace_types __read_mostly; >> >> @@ -3466,6 +3467,47 @@ tracing_entries_write(struct file *filp, const char __user *ubuf, >> return cnt; >> } >> >> +static ssize_t >> +tracing_overwrite_read(struct file *filp, char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + char buf[64]; >> + int r; >> + r = snprintf(buf, 64, "%u\n", trace_buffer_flags); >> + return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); >> +} >> + >> +static ssize_t >> +tracing_overwrite_write(struct file *filp, const char __user *ubuf, >> + size_t cnt, loff_t *ppos) >> +{ >> + unsigned long val; >> + char buf[64]; >> + int ret; >> + >> + if (cnt >= sizeof(buf)) >> + return -EINVAL; >> + >> + if (copy_from_user(&buf, ubuf, cnt)) >> + return -EFAULT; >> + >> + buf[cnt] = 0; >> + >> + ret = strict_strtoul(buf, 10, &val); >> + if (ret < 0) >> + return ret; >> + *ppos += cnt; >> + >> + if (val != 0 && val != 1) >> + return -EINVAL; >> + >> + if (trace_buffer_flags != val) { >> + trace_buffer_flags = val; >> + ring_buffer_change_overwrite(global_trace.buffer, val); >> + } >> + return cnt; >> +} >> + >> static int mark_printk(const char *fmt, ...) >> { >> int ret; >> @@ -3611,6 +3653,12 @@ static const struct file_operations tracing_entries_fops = { >> .llseek = generic_file_llseek, >> }; >> >> +static const struct file_operations tracing_overwrite_fops = { >> + .open = tracing_open_generic, >> + .read = tracing_overwrite_read, >> + .write = tracing_overwrite_write, >> +}; >> + >> static const struct file_operations tracing_mark_fops = { >> .open = tracing_open_generic, >> .write = tracing_mark_write, >> @@ -4336,6 +4384,9 @@ static __init int tracer_init_debugfs(void) >> trace_create_file("buffer_size_kb", 0644, d_tracer, >> &global_trace, &tracing_entries_fops); >> >> + trace_create_file("buffer_overwrite", 0644, d_tracer, >> + &global_trace, &tracing_overwrite_fops); >> + >> trace_create_file("trace_marker", 0220, d_tracer, >> NULL, &tracing_mark_fops); >> >> @@ -4565,7 +4616,7 @@ __init static int tracer_alloc_buffers(void) >> >> /* TODO: make the number of buffers hot pluggable with CPUS */ >> global_trace.buffer = ring_buffer_alloc(ring_buf_size, >> - TRACE_BUFFER_FLAGS); >> + trace_buffer_flags); >> if (!global_trace.buffer) { >> printk(KERN_ERR "tracer: failed to allocate ring buffer!\n"); >> WARN_ON(1); >> @@ -4575,7 +4626,7 @@ __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, trace_buffer_flags); >> if (!max_tr.buffer) { >> printk(KERN_ERR "tracer: failed to allocate max ring buffer!\n"); >> WARN_ON(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/
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