Messages in this thread | | | From | Vaibhav Nagarnaik <> | Date | Fri, 29 Jul 2011 12:10:20 -0700 | Subject | Re: [PATCH 2/5] trace: Add ring buffer stats to measure rate of events |
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On Fri, Jul 29, 2011 at 11:10 AM, Steven Rostedt <rostedt@goodmis.org> wrote: > On Tue, 2011-07-26 at 15:59 -0700, Vaibhav Nagarnaik wrote: >> The stats file under per_cpu folder provides the number of entries, >> overruns and other statistics about the CPU ring buffer. However, the >> numbers do not provide any indication of how full the ring buffer is in >> bytes compared to the overall size in bytes. Also, it is helpful to know >> the rate at which the cpu buffer is filling up. >> >> This patch adds an entry "bytes: " in printed stats for per_cpu ring >> buffer which provides the actual bytes consumed in the ring buffer. This >> field includes the number of bytes used by recorded events and the >> padding bytes added when moving the tail pointer to next page. >> >> It also adds the following time stamps: >> "head ts:" - the oldest timestamp in the ring buffer > > > I hate the name of "head_ts", as it really is meaningless. The head of > our ring buffer is indeed the oldest events, but other ring buffers have > head as the newest. This is an internal name that should not be used > outside of the ring buffer code itself. Maybe call it "oldest_ts", or > even more verbose (and what it actually is), "oldest_event_ts". > > >> "now ts:" - the timestamp at the time of reading >> >> The field "now ts" provides a consistent time snapshot to the userspace >> when being read. This is read from the same trace clock used by tracing >> event timestamps. >> >> Together, these values provide the rate at which the buffer is filling >> up, from the formula: >> bytes / (now_ts - head_ts) >> >> Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com> >> --- > >> /** >> + * ring_buffer_head_ts - get the oldest event timestamp from the buffer >> + * @buffer: The ring buffer >> + * @cpu: The per CPU buffer to read from. >> + */ >> +unsigned long ring_buffer_head_ts(struct ring_buffer *buffer, int cpu) > > Hence, replace head_ts, with something else here. > > Thanks, > > -- Steve >
'oldest_event_ts' sounds good.
Vaibhav Nagarnaik -- 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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