perf/x86/intel: Avoid spamming kernel log for BTS buffer failure

rientjes · Ingo Molnar · commit 4485154138f6 · 2014-07-16T13:31:30.000+02:00
It's unnecessary to excessively spam the kernel log anytime the BTS buffer cannot be allocated, so make this allocation __GFP_NOWARN. The user probably will want to at least find some artifact that the allocation has failed in the past, probably due to fragmentation because of its large size, when it's not allocated at bootstrap. Thus, add a WARN_ONCE() so something is left behind for them to understand why perf commnads that require PEBS is not working properly. Signed-off-by: David Rientjes <rientjes@google.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1406301600460.26302@chino.kir.corp.google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -311,9 +311,11 @@ static int alloc_bts_buffer(int cpu)
 	if (!x86_pmu.bts)
 		return 0;
 
-	buffer = kzalloc_node(BTS_BUFFER_SIZE, GFP_KERNEL, node);
-	if (unlikely(!buffer))
+	buffer = kzalloc_node(BTS_BUFFER_SIZE, GFP_KERNEL | __GFP_NOWARN, node);
+	if (unlikely(!buffer)) {
+		WARN_ONCE(1, "%s: BTS buffer allocation failure\n", __func__);
 		return -ENOMEM;
+	}
 
 	max = BTS_BUFFER_SIZE / BTS_RECORD_SIZE;
 	thresh = max / 16;
