On Thu, Sep 19, 2024 at 5:13 PM Sebastião Amaro <sebassamaro97@xxxxxxxxx> wrote: > > Hi everyone! > I have two questions related to user function probes: > Firstly, I am trying to have a process attach more than 1024 uprobes, > however, I am getting the error: "failed to create BPF link for > perf_event FD 1023: -24 (Too many open files)" even after changing > ulimit -n to 4096 github issue[1]. See [0], it might be that `ulimit -n` isn't really changing the limit for your process or something. To be 100% sure I'd do setrlimit(RLIMIT_NOFILE, ...) from inside the process to verify. [0] https://unix.stackexchange.com/questions/8945/how-can-i-increase-open-files-limit-for-all-processes > Secondly, I am running some tests with uprobe and uprobe_ret in multiple > functions in the redis binary, but I am noticing that when counting the > times the uprobes and uprobes_ret are called, in the end they do not > match 1 to 1. Either individually (a uprobe/uprobe_ret in the same > function), or the total sum. Is this a predictable behaviour? > I am tracing several functions in such as [2]. Attachment is not atomic, so you might get some uprobes attached before corresponding uretprobe is attached, and vice versa. So counts might not match 1:1 during attachment and detachment. > > [1]https://github.com/libbpf/libbpf-rs/issues/942 > [2]https://github.com/redis/redis/blob/3a3cacfefabf8ced79b448169319ce49cca2bfb7/src/rdb.c#L1782 > > Thank you, and Best Regards, > Sebastião Amaro >
