From mboxrd@z Thu Jan  1 00:00:00 1970
From: Brendan Gregg <brendan.d.gregg-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH RFC v4 net-next 00/26] BPF syscall, maps, verifier,
 samples, llvm
Date: Thu, 14 Aug 2014 12:17:39 -0700
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To: Alexei Starovoitov <ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org>
Cc: "David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>, Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Daniel Borkmann <dborkman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Chema Gonzalez <chema-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Eric Dumazet <edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>, "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
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On Wed, Aug 13, 2014 at 12:57 AM, Alexei Starovoitov <ast-uqk4Ao+rVK5Wk0Htik3J/w@public.gmane.org> wrote:
[...]
> Tracing use case got some improvements as well. Now eBPF programs can be
> attached to tracepoint, syscall, kprobe and C examples are more usable:
> ex1_kern.c - demonstrate how programs can walk in-kernel data structures
> ex2_kern.c - in-kernel event accounting and user space histograms
> See patch #25

This is great, thanks! I've been using this new support, and
successfully ported an an older tool of mine (bitesize) to eBPF. I was
using the block:block_rq_issue tracepoint, and performing a custom
in-kernel histogram, like in the ex2_kern.c example, for I/O size.

I also did some quick overhead testing and found eBPF with JIT to be
relatively fast. (I'd share numbers but it's platform specific.) The
syscall tracepoints were a bit slower than hoped, for what I think is
a well known issue.

Are there thoughts in general for how this might be used for embedded
devices, where installing clang/llvm might be prohibitive? Compile on
another system and move the binaries over? thanks,

Brendan