On 04/03/2020 07:48, Dixit, Ashutosh wrote:
On Tue, 03 Mar 2020 14:19:05 -0800, Umesh Nerlige Ramappa wrote:
From: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
With the currently available parameters for the i915-perf stream,
there are still situations that are not well covered :
If an application opens the stream with polling disable or at very low
frequency and OA interrupt enabled, no data will be available even
though somewhere between nothing and half of the OA buffer worth of
data might have landed in memory.
To solve this issue we have a new flush ioctl on the perf stream that
forces the i915-perf driver to look at the state of the buffer when
called and makes any data available through both poll() & read() type
syscalls.
v2: Version the ioctl (Joonas)
v3: Rebase (Umesh)
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
[snip]
+/**
+ * i915_perf_flush_data - handle `I915_PERF_IOCTL_FLUSH_DATA` ioctl
+ * @stream: An enabled i915 perf stream
+ *
+ * The intention is to flush all the data available for reading from the OA
+ * buffer
+ */
+static void i915_perf_flush_data(struct i915_perf_stream *stream)
+{
+ stream->pollin = oa_buffer_check(stream, true);
+}
Since this function doesn't actually wake up any thread (which anyway can
be done by sending a signal to the blocked thread), is the only purpose of
this function to update OA buffer head/tail? But in that it is not clear
why a separate ioctl should be created for this, can't the read() call
itself call oa_buffer_check() to update the OA buffer head/tail?
Again just trying to minimize uapi changes if possible.
Most applications will call read() after being notified by
poll()/select() that some data is available.
Changing that behavior will break some of the existing perf tests .
If any data is available, this new ioctl will wake up existing waiters
on poll()/select().
-Lionel
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