Messages in this thread | | | From | Alexei Starovoitov <> | Date | Thu, 29 Jan 2015 10:55:07 -0800 | Subject | Re: [PATCH v2 linux-trace 1/8] tracing: attach eBPF programs to tracepoints and syscalls |
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On Thu, Jan 29, 2015 at 4:35 AM, Namhyung Kim <namhyung@kernel.org> wrote: >>> Right. I think bpf programs belong to a user process but events are >>> global resource. Maybe you also need to consider attaching bpf >>> program via perf (ioctl?) interface.. >> >> yes. I did. Please see my reply to Masami. >> ioctl only works for tracepoints. > > What was the problem of kprobes then? :)
Looks like I misread the logic of attaching a filter via perf ioctl. Looking at it again it seems to be a major change in design: Instead of adding into ftrace_raw_* helpers, I would add to perf_trace_* helpers which are very stack heavy because of 'pt_regs' Ex: perf_trace_kfree_skb() is using 224 bytes of stack whereas ftrace_raw_event_kfree_skb() only 80. which doesn't help in my quest for lowest overhead. And the discussion about soft- and auto- enable/disable becomes meaningless, since there is no such things when it goes through perf events. I guess it means no hooks through tracefs... Anyway, I'll hook it up and see which way is cleaner.
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