On Wed, 5 Apr 2023 at 00:33, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > 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 very much for the quick answer! > > > > Thank you in advance for your time, > > Andrea > > > > 0: https://github.com/torvalds/linux/commit/fec56f5890d93fc2ed74166c397dc186b1c25951
