From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Wangnan (F)" Subject: Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling Date: Thu, 22 Oct 2015 11:12:16 +0800 Message-ID: <56285410.3060505@huawei.com> References: <1445325735-121694-1-git-send-email-xiakaixu@huawei.com> <1445325735-121694-2-git-send-email-xiakaixu@huawei.com> <5626C5CE.8080809@plumgrid.com> <20151021091254.GF2881@worktop.programming.kicks-ass.net> <56276968.6070604@huawei.com> <20151021113316.GM17308@twins.programming.kicks-ass.net> <56277BCE.6030400@huawei.com> <20151021121713.GC3604@twins.programming.kicks-ass.net> <56279634.5000606@huawei.com> <5628423B.4010504@huawei.com> <5628535F.5060505@plumgrid.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Cc: xiakaixu , , , , , , , , , , To: Alexei Starovoitov , Peter Zijlstra Return-path: In-Reply-To: <5628535F.5060505@plumgrid.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 2015/10/22 11:09, Alexei Starovoitov wrote: > 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? Yes. > What pt_regs would be in such case? > Sampling is based on interruption. We can use pt_reg captured by the IRQ handler, or we can simply pass NULL to those BPF program. Thank you.