wakeup_events and sample_period is set to 1. what is the reason for this?
Isn't it better if this number is higher so the polling doesn't happen
all the time?
what is "sample_period" if wakeup_events tells kernel to wake up.
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Please correct me if I'm wrong about anything.
When a perf_event is attached to a BPF program and the BPF program is
going to do processing and then output what is the significant of
wakeup_events or wakeup_watermark for the original perf_event?
To me it seem like it BPF program will always run,
I should have search. Short answer it fails and you're out of luck.
https://lists.iovisor.org/g/iovisor-dev/topic/accessing_user_memory_and/21386221
On Sun, Feb 16, 2020 at 9:29 PM Hayden Livingston
wrote:
>
> I'm curios to know how bpf_probe_read is able to read user-mode
I'm curios to know how bpf_probe_read is able to read user-mode memory
in the face of page faulting.
I know in the helper it disables page faulting, but what does that mean?
If the memory the probe is trying to read is paged out then how does
my probe work?
It seems bpf_probe_read is best
Imagine I have a per-cpu perf ring buffer for all my cpus.
Now I have two eBPF programs.
In both these eBPF programs I do bpf_update_elem(myFD, ,
, BPF_ANY)
Will this mean that multiple eBPF programs will be able to write their
data into a single buffer (of course associated with cpu).
This
directly.
On Sun, Feb 16, 2020 at 1:50 PM Y Song wrote:
>
> PERF_EVENT_OUTPUT map is to hold per cpu ring buffers created by
> perf_event_open.
> That is why its typical size is the number of cpus on the host.
>
> On Sun, Feb 16, 2020 at 1:52 AM Hayden Livingston
> wrote:
> >
I'm very confused why BCC creates a map of number of processors for
the perf_events output map.
I can imagine it being 1 since all it does is act as a kernel-user
mode intermediary and it is true that the code cannot be preempted.
Or if it can be preempted then I can imagine that since there
