Tests: Test snapshot maximum size correctly

The minimum size for a channel is determined by:

  sub-buffer-size * sub-buffer-count * possible-cpus

where sub-buffer-size is the system page size and sub-buffer-count is 2.

We set a snapshot with a maximum size of the minimum size. From there,
we need to spam that amount of events, assuming each event to be one
byte, on every online CPUs. We can then ensure that the total snapshot's
size is equal to the minimum size for a channel. However, there's a
little bias if the number of possible cores is greater than the number
of online cores. In that case, the bias is one sub-buffer for each extra
ring buffer.

Change-Id: I4718e134684463789b4f7be9b12c9bf3d6cfec20
Signed-off-by: Olivier Dion <odion@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/tests/regression/tools/snapshots/ust_test b/tests/regression/tools/snapshots/ust_test
index 7eff6df5ee79b7847976d4255bf9741631fd3512..e6a463bce0984abd3ae2bcb14e2cee0f903a63bd 100755 (executable)
--- a/tests/regression/tools/snapshots/ust_test
+++ b/tests/regression/tools/snapshots/ust_test
@@ -16,7 +16,7 @@ TESTAPP_NAME="gen-ust-events"
 TESTAPP_BIN="$TESTAPP_PATH/$TESTAPP_NAME/$TESTAPP_NAME"
 APPS_PID=
 
-NUM_TESTS=105
+NUM_TESTS=104
 
 TRACE_PATH=$(mktemp -d)
 
@@ -109,9 +109,11 @@ function enable_mmap_overwrite_subbuf_ust_channel ()
        local sess_name=$1
        local chan_name=$2
        local subbuf_size=$3
+       local subbuf_count=$4
 
        $TESTDIR/../src/bin/lttng/$LTTNG_BIN enable-channel -s $sess_name \
                $chan_name -u --output mmap --overwrite \
+               --num-subbuf=$subbuf_count \
                --subbuf-size $subbuf_size > /dev/null 2>&1
 
        ok $? "Enable channel $channel_name for session $sess_name with subbuf size $subbuf_size"
@@ -295,53 +297,65 @@ function test_ust_local_snapshot_small_overwrite_buffers ()
 
 function test_ust_local_snapshot_max_size ()
 {
-       NR_ITER=-1
-       NR_USEC_WAIT=100
-       page_size=`getconf PAGE_SIZE`
-       num_cpus=$(conf_proc_count)
-
-       # The minimum subbuf size is the platform PAGE_SIZE
-       subbuf_size=$(($page_size*2))
-
-       # The minimum size limit is min(subbuf_size) * nb_streams
-       max_size=$(($subbuf_size*$num_cpus))
+       local possible_cpus
+       local online_cpus
+       local subbuf_size
+       local subbuf_count
+       local snapshot_max_size
+       local channel_max_size_per_cpu
+
+       possible_cpus=$(get_possible_cpus_count)
+       online_cpus=$(conf_proc_count)
+       subbuf_size=$(getconf PAGE_SIZE)
+       subbuf_count=8
+       snapshot_max_size=$((subbuf_size*possible_cpus))
+       channel_max_size_per_cpu=$((subbuf_size*subbuf_count))
 
        diag "Test local UST snapshots with max size $max_size"
-       create_lttng_session_no_output $SESSION_NAME
+       create_lttng_session_no_output "$SESSION_NAME"
 
-       enable_mmap_overwrite_subbuf_ust_channel $SESSION_NAME $CHANNEL_NAME $subbuf_size
+       enable_mmap_overwrite_subbuf_ust_channel \
+               "$SESSION_NAME" "$CHANNEL_NAME" \
+               "$subbuf_size" "$subbuf_count"
 
-       enable_ust_lttng_event_ok $SESSION_NAME $EVENT_NAME $CHANNEL_NAME
-       start_lttng_tracing_ok $SESSION_NAME
+       enable_ust_lttng_event_ok "$SESSION_NAME" "$EVENT_NAME" "$CHANNEL_NAME"
+       start_lttng_tracing_ok "$SESSION_NAME"
 
-       snapshot_add_output $SESSION_NAME "file://$TRACE_PATH" "" $max_size
+       snapshot_add_output "$SESSION_NAME" "file://$TRACE_PATH" "" "$snapshot_max_size"
 
-       # Returns once the application has at least fired ONE tracepoint.
-       start_test_app
+       # Fill all ring-buffers of the channel; assuming event size of at least one
+       # byte
+       for cpu in $(seq "$online_cpus");
+       do
+               taskset --cpu-list $((cpu-1)) "$TESTAPP_BIN" \
+                       --iter "$channel_max_size_per_cpu"
+       done
+       diag "Filled channel ring-buffers"
 
-       lttng_snapshot_record $SESSION_NAME
+       lttng_snapshot_record "$SESSION_NAME"
 
        # Check file size
-       sum_size_tracefiles=$(find $TRACE_PATH -name "${CHANNEL_NAME}_*" \
-               -exec stat -c '%s' {} \; | awk '{s = s + $1}END{print s}')
+       local snapshot_size
+       snapshot_size=$(find "$TRACE_PATH" -name "${CHANNEL_NAME}_*" \
+                               -exec stat -c '%s' {} \; | \
+                               awk '{s = s + $1}END{print s}')
 
-       if [ "$sum_size_tracefiles" -gt "$max_size" ]; then
-               fail "Tracefiles size sum validation"
-               diag "Tracefiles size sum: $sum_size_tracefiles Expected max: $max_size"
-       else
+       if [ "$snapshot_size" -eq "$snapshot_max_size" ]; then
                pass "Tracefiles size sum validation"
+       else
+               fail "Tracefiles size sum validation"
+               diag "Tracefiles size sum: $snapshot_size Expected max: $snapshot_max_size"
        fi
 
-       stop_lttng_tracing_ok $SESSION_NAME
-       destroy_lttng_session_ok $SESSION_NAME
+       stop_lttng_tracing_ok "$SESSION_NAME"
+       destroy_lttng_session_ok "$SESSION_NAME"
 
        # Validate test
        validate_trace_path_ust_uid_snapshot "$TRACE_PATH" "" "snapshot-1" 0
-       validate_trace $EVENT_NAME $TRACE_PATH/
 
-       if [ $? -eq 0 ]; then
+       if validate_trace "$EVENT_NAME" "$TRACE_PATH/"; then
                # Only delete if successful
-               rm -rf $TRACE_PATH
+               rm -rf "$TRACE_PATH"
        fi
 
        stop_test_apps