Re: [PATCH v3 bpf-next 1/4] tracing/probe: Add PERF_EVENT_IOC_QUERY_PROBE ioctl

From: Yonghong Song
Date: Wed Aug 21 2019 - 18:12:16 EST




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
>