On Wed, 12 Jan 2022 16:33:53 +0900 Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > Hi Alexei, > > On Tue, 11 Jan 2022 14:39:44 -0800 > Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > > On Wed, Jan 12, 2022 at 12:00:17AM +0900, Masami Hiramatsu wrote: > > > Hi Jiri, > > > > > > Here is a short series of patches, which shows what I replied > > > to your series. > > > > > > This introduces the fprobe, the function entry/exit probe with > > > multiple probe point support. This also introduces the rethook > > > for hooking function return, which I cloned from kretprobe. > > > > > > I also rewrite your [08/13] bpf patch to use this fprobe instead > > > of kprobes. I didn't tested that one, but the sample module seems > > > to work. Please test bpf part with your libbpf updates. > > > > > > BTW, while implementing the fprobe, I introduced the per-probe > > > point private data, but I'm not sure why you need it. It seems > > > that data is not used from bpf... > > > > > > If this is good for you, I would like to proceed this with > > > the rethook and rewrite the kretprobe to use the rethook to > > > hook the functions. That should be much cleaner (and easy to > > > prepare for the fgraph tracer integration) > > > > What is the speed of attach/detach of thousands fprobes? > > I've treaked my example module and it shows below result; > > /lib/modules/5.16.0-rc4+/kernel/samples/fprobe # time insmod ./fprobe_example.ko > symbol='btrfs_*' > [ 187.095925] fprobe_init: 1028 symbols found > [ 188.521694] fprobe_init: Planted fprobe at btrfs_* > real 0m 1.47s > user 0m 0.00s > sys 0m 1.36s > > I think using ftrace_set_filter_ips() can make it faster. > (maybe it needs to drop per-probe point private data, that > prevents fprobe to use that interface) OK, I've updated fprobes to use the ftrace_set_filter_ips() and got below result. /lib/modules/5.16.0-rc4+/kernel/samples/fprobe # time insmod fprobe_example.ko s ymbol='btrfs_*' [ 36.130947] fprobe_init: 1028 symbols found [ 36.177901] fprobe_init: Planted fprobe at btrfs_* real 0m 0.08s user 0m 0.00s sys 0m 0.07s Let me update the series :) Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
