On Fri, Mar 31, 2023 at 4:32 AM andrea terzolo <andreaterzolo3@xxxxxxxxx> wrote: > > Hello! If I can I would like to ask one question about the BPF > trampoline. Reading the description of this commit [0] I noticed the > following statement: > > - Detach of a BPF program from the trampoline should not fail. To avoid memory > allocation in detach path the half of the page is used as a reserve and flipped > after each attach/detach. 2k bytes is enough to call 40+ BPF programs directly > which is enough for BPF tracing use cases. This limit can be increased in the > future. > > Looking at the kernel code, I found only this limit > BPF_MAX_TRAMP_LINKS. If I understood correctly, this limit denies us > the use of the same trampoline for more than 38 bpf programs. So my > question is, does the commit description refer to another limit or > does this "call 40+ BPF programs" refer to the BPF_MAX_TRAMP_LINKS > macro? No, it's BPF_MAX_TRAMP_LINKS, which got reduced a bit down from its 40+ limit to current 38. > > Thank you in advance for your time, > Andrea > > 0: https://github.com/torvalds/linux/commit/fec56f5890d93fc2ed74166c397dc186b1c25951
