linux-kernel - [patch] x86, perf: avoid spamming kernel log for bts buffer failure

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Date:	Mon, 30 Jun 2014 16:04:08 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
cc:	Stephane Eranian <eranian@...gle.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [patch] x86, perf: avoid spamming kernel log for bts buffer
 failure

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@...gle.com>
---
 arch/x86/kernel/cpu/perf_event_intel_ds.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
--- 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;
--
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