netdev - Re: [PATCH v6 perf,bpf 06/15] perf, bpf: save bpf_prog_info in a rbtree in perf

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Date:   Thu, 7 Mar 2019 15:05:46 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        kernel-team@...com, peterz@...radead.org, acme@...hat.com,
        jolsa@...nel.org, namhyung@...nel.org
Subject: Re: [PATCH v6 perf,bpf 06/15] perf, bpf: save bpf_prog_info in a
 rbtree in perf_env

On Tue, Mar 05, 2019 at 11:13:50PM -0800, Song Liu wrote:
> bpf_prog_info contains information necessary to annotate bpf programs.
> This patch saves bpf_prog_info for bpf programs loaded in the system.
> 
> Some big picture of the next few patches:
> 
> To fully annotate BPF programs with source code mapping, 4 different
> information are needed:
>     1) PERF_RECORD_KSYMBOL
>     2) PERF_RECORD_BPF_EVENT
>     3) bpf_prog_info
>     4) btf
> 
> Before this set, 1) and 2) in the list are already saved to perf.data
> file. For BPF programs that are already loaded before perf run, 1) and 2)
> are synthesized by perf_event__synthesize_bpf_events(). For short living
> BPF programs, 1) and 2) are generated by kernel.
> 
> This set handles 3) and 4) from the list. Again, it is necessary to handle
> existing BPF program and short living program separately.
> 
> This patch handles 3) for exising BPF programs while synthesizing 1) and
> 2) in perf_event__synthesize_bpf_events(). These data are stored in
> perf_env. The next patch saves these data from perf_env to perf.data as
> headers.
> 
> Similarly, the two patches after the next saves 4) of existing BPF
> programs to perf_env and perf.data.
> 
> Another patch later will handle 3) and 4) for short living BPF programs
> by monitoring 1) and 2) in a dedicate thread.
> 

thanks for the changelog

SNIP

> +
> +		/* save bpf_prog_info to env */
> +		info_node = malloc(sizeof(struct bpf_prog_info_node));
> +
> +		/*
> +		 * Do not bail out for !info_node, as we still want to
> +		 * call  perf_tool__process_synth_event()
> +		 */

well, we are out of memory, so I dont think perf_tool__process_synth_event
will get too far.. also the perf_env data would be inconsistent with what
you store as event.. how can that work?

jirka

> +		if (info_node) {
> +			info_node->info_linear = info_linear;
> +			perf_env__insert_bpf_prog_info(env, info_node);
> +			info_linear = NULL;
> +		}

SNIP