linux-kernel - Re: [PATCH v3 bpf-next 1/4] tracing/probe: Add PERF_EVENT_IOC_QUERY

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Date:   Wed, 21 Aug 2019 22:10:58 +0000
From:   Yonghong Song <yhs@...com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
CC:     Peter Zijlstra <peterz@...radead.org>, Daniel Xu <dxu@...uu.xyz>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Song Liu <songliubraving@...com>,
        Andrii Nakryiko <andriin@...com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        Alexei Starovoitov <ast@...com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>
Subject: Re: [PATCH v3 bpf-next 1/4] tracing/probe: Add
 PERF_EVENT_IOC_QUERY_PROBE ioctl



On 8/21/19 1:07 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Aug 21, 2019 at 04:54:47PM +0000, Yonghong Song escreveu:
>> Arnaldo has a question on bcc mailing list about the hit/miss
>> counting of bpf program missed to process events.
>   
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.iovisor.org_g_iovisor-2Ddev_message_1783&d=DwIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=Rrvq6K3mx2wYBCU6cSXLjJj8Xfb06oymxNZH8ysnlLA&s=IbEaX8v0OulmvKU-pmcAhWNmaHwXgaDd5auVFfRoyJg&e=
> 
> PERF_FORMAT_LOST seems to be a good answer to that? See my other reply
> to this thread.

Just checked. indeed adding PERF_FORMAT_LOST to perf read_format
seems a reasonable approach. ioctl with perf_event_open fd can do the 
same thing, but ioctl should be avoided if we have alternatives.

Thanks for the pointer!

> 
> - Arnaldo
>