On 3/28/18 6:49 AM, Mathieu Desnoyers wrote:
----- On Mar 27, 2018, at 10:11 PM, Alexei Starovoitov ast@xxxxxx wrote:
From: Alexei Starovoitov <ast@xxxxxxxxxx>
compute number of arguments passed into tracepoint
at compile time and store it as part of 'struct tracepoint'.
The number is necessary to check safety of bpf program access that
is coming in subsequent patch.
Hi Alexei,
Given that only eBPF needs this parameter count, we can move
it to the struct bpf_raw_event_map newly introduced by Steven,
right ? This would reduce bloat of struct tracepoint. For instance,
we don't need to keep this count around when eBPF is configured
out.
Makes sense. That is indeed cleaner. Will respin.
What I don't like though is 'bloat' argument.
'u32 num_args' padded to 8-byte takes exactly the same amount
of space in 'struct tracepoint' and in 'struct bpf_raw_event_map'
The number of these structures is the same as well
and chances that tracepoints are on while bpf is off are slim.
More so few emails ago you said:
"I'm perfectly fine with adding the "num_args" stuff. I think it's
really useful. It's only the for_each_kernel_tracepoint change for
which I'm trying to understand the rationale."
I'm guessing now you found out that num_args is not useful to lttng
and it bloats its data structures?
It's ok to change an opinion and I'm completely fine using that as
a real reason.
Will repsin, as I said. No problem.
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