perf top: Display slow reader warning when droping samples

Currently we display the "Too slow to read ring buffer.." helpline only
in the slow reader thread. This patch triggers it also when the
processing thread drops samples, because it has the same reason, which
is too many data on input.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NNamhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-bnev2mloavyurmgchcr3o24o@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-top.c

@@ -571,7 +571,7 @@ static void perf_top__sort_new_samples(void *arg)
 	hists__collapse_resort(hists, NULL);
 	perf_evsel__output_resort(evsel, NULL);
 
-	if (t->lost)
+	if (t->lost || t->drop)
 		pr_warning("Too slow to read ring buffer (change period (-c/-F) or limit CPUs (-C)\n");
 
 	perf_top__reset_sample_counters(t);