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

David Rientjes
2014-07-14T23:33:53Z

On Mon, 30 Jun 2014, David Rientjes wrote:

> 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>

Peter, would you like to ack this? Trying to get this merged in time for
the next merge window.

> ---
> 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;