perf/x86/intel: 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@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
index 980970cb744db6793a0f355f092db0e4a17b6ec5..696ade311ded7d01103323d159cff621b46d4a89 100644 (file)
--- 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;