linux-kernel - Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling

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Message-ID: <5628535F.5060505@plumgrid.com>
Date:	Wed, 21 Oct 2015 20:09:19 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	xiakaixu <xiakaixu@...wei.com>, davem@...emloft.net,
	acme@...nel.org, mingo@...hat.com, masami.hiramatsu.pt@...achi.com,
	jolsa@...nel.org, daniel@...earbox.net,
	linux-kernel@...r.kernel.org, pi3orama@....com, hekuang@...wei.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY
 maps trace data output when perf sampling

On 10/21/15 6:56 PM, Wangnan (F) wrote:
>> One alternative solution I can image is to attach a BPF program
>> at sampling like kprobe, and return 0 if we don't want sampling
>> take action. Thought?
>
> Do you think attaching BPF programs to sampling is an acceptable idea?

If you mean to extend 'filter' concept to sampling events?
So instead of soft_disable of non-local events, you'll attach bpf
program to sampling events and use map lookup to decide whether
to filter out or not such sampling event?
What pt_regs would be in such case?

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