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Is there a reason why map.increment() internally copies the key into a stack variable? When building a key inline, it uses double the stack space and incurs the cost of a copy. For u64 keys this is

By Donald Hunter · #1993 ·

Re: [libbpf] Questions about XDP/TC

chenhengqi@... writes: libbpf does not yet support attaching to TC hooks, but there is work in progress to add this.

By Toke Høiland-Jørgensen · #1992 ·

[libbpf] Questions about XDP/TC

1. How do I attach `BPF_PROG_TYPE_SCHED_CLS`/`classifier` BPF programs to specific data path(i.e. ingress or egress) using libbpf ? I found some comments related in the source: ``` The

By chenhengqi@... · #1991 ·

Re: libffi trampolines and stack traces? : was Overly brief stack traces for Java/linux ?

Thanks for your help with this - and for the sketch of how to proceed with it. I'm going to look into the feasibility of fixing the frame pointer in the trampoline before attempting what you have

By Bradley Schatz · #1990 ·

Re: libffi trampolines and stack traces? : was Overly brief stack traces for Java/linux ?

<ys114321=gmail.com@...> wrote: I briefly looked at the perf and kernel code and experimented with perf dwarf mode. It is possible for bpf to copy user stack to user space. You could

By Yonghong Song · #1989 ·

Re: libffi trampolines and stack traces? : was Overly brief stack traces for Java/linux ?

<bradley@...> wrote: The bpf stack unwinder is using the kernel one which is the frame pointer based and it may have issues with generated trampoline code which may mess up frame

By Yonghong Song · #1988 ·

libffi trampolines and stack traces? : was Overly brief stack traces for Java/linux ?

I still digging into this issue, and have hacked memleak/bcc to show addresses when they cant be resolved. In other places, I'm seeing jit complied java stack frames showing up alongside C ones, which

By Bradley Schatz · #1987 ·

Re: Overly brief stack traces for Java/linux ?

The file perf-18047.map is there and from other parts of the stack trace I can see it being used to successfully resolve symbols. Thanks! On 7/4/21, 4:44 am, "Y Song" <ys114321@...>

By Bradley Schatz · #1986 ·

Re: Overly brief stack traces for Java/linux ?

<bradley@...> wrote: I have no experience with perf-map-agent, but the following is what I guess: [perf-18047.map] is used to find the mapping between address and symbol. What does

By Yonghong Song · #1985 ·

LPC 2021 Networking and BPF Track CFP

We are pleased to announce the Call for Proposals (CFP) for the Networking and BPF track at the 2021 edition of the Linux Plumbers Conference (LPC), which is planned to be held in Dublin, Ireland, on

By Daniel Borkmann · #1984 ·

Re: Overly brief stack traces for Java/linux ?

Thanks for the suggestion. I found a tunable to keep the JNI shared library in memory after loading. As you can see below, it is no longer showing as deleted. 13238272 bytes in 404 allocations from

By Bradley Schatz · #1983 ·

Re: Overly brief stack traces for Java/linux ?

<bradley@...> wrote: I can see the file has been marked as deleted. 34603008 bytes in 33 allocations from stack [unknown] [jna9005484735610534564.tmp (deleted)]

By Yonghong Song · #1982 ·

Overly brief stack traces for Java/linux ?

Hi, I’m just starting to come to grips with bcc & perf-map-agent for introspecting java on linux, with the goal of identifying what appears to be an off-heap memory leak (using memleak). I

By Bradley Schatz · #1981 ·

Re: Questions about runqlen

Hi Y Song, Loop is forbidden in BPF programs (although bounded loop is supported from linux-5.3, tracking down to NULL se->parent is un-bounded). Maybe it's worth trying to get the definition

By Abel Wu · #1980 ·

Re: Questions about runqlen

Could you file an "issue" for the question? This issue, the questions/answers can be easily tracked. There are some answers in this issue: https://github.com/iovisor/bcc/issues/3093 To be accurate

By Yonghong Song · #1979 ·

Re: BCC and passing packet from XDP to user-mode app #bcc

<federico.parola@...> wrote: Thanks, Federico and others. Maybe one of you can add it to the reference_guide.md? We do have events.perf_submit there. Thanks!

By Yonghong Song · #1978 ·

Re: BCC and passing packet from XDP to user-mode app #bcc

Hi, the virtual function you are looking for is perf_submit_skb(): https://github.com/iovisor/bcc/blob/c8de00e1746e242cdcd68b4673a083bb467cd35e/src/cc/export/helpers.h#L193 Strangely it is not

By Federico Parola · #1977 ·

BCC and passing packet from XDP to user-mode app #bcc

Hi! Is it possible to pass full ethernet packet from XDP to user-mode app using BCC? I wrote C code like this: BPF_PERF_OUTPUT(captured_data); int capture(struct xdp_md *ctx) {

By v.a.bonert@... · #1976 · Edited

Re: Which file should I include for KERNEL_VERSION macro ?

It will soon be part of bpf_helpers.h, but meanwhile just copy/paste it into your code. See https://patchwork.kernel.org/project/netdevbpf/patch/20210317200510.1354627-2-andrii@.../ >

By Andrii Nakryiko · #1975 ·

Which file should I include for KERNEL_VERSION macro ?

I'v read this blog post https://facebookmicrosites.github.io/bpf/blog/2020/02/19/bpf-portability-and-co-re.html And want to apply this technique to my program:

By chenhengqi@... · #1974 ·

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