On Tue, Aug 9, 2016 at 9:16 AM, riya khanna <[email protected]> wrote:
> On Tue, Aug 9, 2016 at 12:05 PM, Brenden Blanco <[email protected]> > wrote: > > On Tue, Aug 9, 2016 at 8:54 AM, riya khanna <[email protected]> > > wrote: > >> > >> Hi Brenden, > >> > >> Saw test_perf_event.py in your branch. Its creates and enables per > >> counters once during start. Is it also possible to > >> enable/disable/reset counters on the fly? Perhaps we need a kernel > >> patch for this? > > > > It doesn't "create" counters, it just attaches to the already available > > counters provided by the hardware or OS. > > Yes, it enables monitoring when attached. > > > Any type of "reset" infrastructure > > would adversely impact other users of those same counters (perf). I > consider > > it the job of userspace or the program to compute deltas or other types > of > > history. > > Well, there are limited counters. How to multiplex from userspace on > the fly (e.g. monitoring a set of events first, followed by a > different set)? I would just create a different BPF_PERF_ARRAY for each different one. > Also, is it possible to handle counter overflow? > What does it mean to "handle"? If computing deltas, for instance, the subtraction will just underflow and wrap around to the correct value, assuming the values are both unsigned. > > >> > >> > >> Thanks, > >> Riya > >> > >> On Fri, Jul 29, 2016 at 1:57 PM, riya khanna <[email protected]> > >> wrote: > >> > Thanks Brenden! > >> > > >> > I'm working with your branch for now. Additionally, I'm unable to > >> > create software events (see exception below). Just wanted to bring > >> > this to your attention. > >> > > >> > Traceback (most recent call last): > >> > > >> > File "./test_bpf.py", line 176, in <module> > >> > sw_clock.open_perf_event(1, 0) > >> > > >> > File "/usr/lib/python2.7/dist-packages/bcc/table.py", line 410, in > >> > open_perf_event > >> > fd = self._open_perf_event(typ, config, i) > >> > File "/usr/lib/python2.7/dist-packages/bcc/table.py", line 416, in > >> > _open_perf_event > >> > self[self.Key(cpu)] = self.Leaf(fd) > >> > File "/usr/lib/python2.7/dist-packages/bcc/table.py", line 320, in > >> > __setitem__ > >> > super(ArrayBase, self).__setitem__(key, leaf) > >> > File "/usr/lib/python2.7/dist-packages/bcc/table.py", line 169, in > >> > __setitem__ > >> > raise Exception("Could not update table") > >> > Exception: Could not update table > >> > > >> > On Fri, Jul 29, 2016 at 1:34 PM, Brenden Blanco <[email protected] > > > >> > wrote: > >> >> On Fri, Jul 29, 2016 at 10:21 AM, riya khanna > >> >> <[email protected]> > >> >> wrote: > >> >>> > >> >>> I'm testing perf counters on a 8-core machine. > >> >>> > >> >>> since BPF_PERF_ARRAY.perf_read(cpu) reads from local CPU, I'm > >> >>> aggregating counters across all cpus by doing: > >> >>> > >> >>> BPF_PERF_ARRAY(counter, 32); > >> >>> > >> >>> for (key = 0; key < 8; key++) > >> >>> counter.perf_read(key); > >> >> > >> >> > >> >> I think it would make more sense to only read the counter on the cpu > >> >> where > >> >> the event is taking place. So: > >> >> > >> >> u64 key = cycles.perf_read(bpf_get_smp_processor_id()); > >> >> > >> >> And then aggregate counters in userspace. > >> >> > >> >> I have spent some time over the past couple days cleaning up the code > >> >> in > >> >> that private branch, but have been distracted a bit so haven't > >> >> finalized it. > >> >> Hopefully a PR will come soon. > >> >> > >> >>> > >> >>> However, this reports error: > >> >>> > >> >>> bpf: Invalid argument > >> >>> back-edge from insn 69 to 17 > >> >>> > >> >>> If I loop from 0-4, it works. The code below works: > >> >>> for (key = 0; key < 4; key++) > >> >>> counter.perf_read(key); > >> >>> > >> >>> > >> >>> What could be wrong here? > >> >> > >> >> The kernel verifier won't allow loops (i.e. back edges), and > depending > >> >> on > >> >> the loop unroll optimization decision made by llvm, this short loop > may > >> >> have > >> >> been automatically unrolled. Still, the solution should be to remove > >> >> the > >> >> loop and just read the local cpu's perf counter as mentioned above. > >> >>> > >> >>> > >> >>> > >> >>> On Tue, Jul 26, 2016 at 7:29 PM, riya khanna > >> >>> <[email protected]> > >> >>> wrote: > >> >>> > From your patches I see that perf support is enabled per-cpu. > Could > >> >>> > this be extended to enabling all or a group of perf counters on > all > >> >>> > CPU cores similar to what perf_event_open provides (with args -1)? > >> >>> > > >> >>> > On Mon, Jul 25, 2016 at 9:55 PM, riya khanna > >> >>> > <[email protected]> > >> >>> > wrote: > >> >>> >> Thanks Brenden! > >> >>> >> > >> >>> >> I will try with your changes. Meanwhile please let me know if you > >> >>> >> add > >> >>> >> missing functionality. > >> >>> >> > >> >>> >> > >> >>> >> On Mon, Jul 25, 2016 at 8:14 PM, Brenden Blanco > >> >>> >> <[email protected]> > >> >>> >> wrote: > >> >>> >>> This needs support in bcc. > >> >>> >>> > >> >>> >>> I had a patch laying around that I never finished, you can find > >> >>> >>> the > >> >>> >>> partial > >> >>> >>> support here: > >> >>> >>> https://github.com/iovisor/bcc/tree/perf-counter > >> >>> >>> > >> >>> >>> It shouldn't be too hard to finalize that, let me see what I can > >> >>> >>> do. > >> >>> >>> > >> >>> >>> On Mon, Jul 25, 2016 at 4:11 PM, riya khanna via iovisor-dev > >> >>> >>> <[email protected]> wrote: > >> >>> >>>> > >> >>> >>>> So I fixed the error above by using "count = > >> >>> >>>> my_map.perf_read(key);" > >> >>> >>>> as opposed to "count = bpf_perf_event_read(&my_map, key);". > >> >>> >>>> However, > >> >>> >>>> how do I selectively enable counters (e.g. instructions, cache > >> >>> >>>> misses, > >> >>> >>>> etc.)? > >> >>> >>>> > >> >>> >>>> Thanks, > >> >>> >>>> Riya > >> >>> >>>> > >> >>> >>>> On Mon, Jul 25, 2016 at 9:58 AM, riya khanna > >> >>> >>>> <[email protected]> > >> >>> >>>> wrote: > >> >>> >>>> > Hi, > >> >>> >>>> > > >> >>> >>>> > I'm trying to read perf counters using bpf. However, adding > >> >>> >>>> > BPF_PERF_ARRAY reports error: > >> >>> >>>> > > >> >>> >>>> > bpf: Invalid argument > >> >>> >>>> > unrecognized bpf_ld_imm64 inns > >> >>> >>>> > > >> >>> >>>> > Is there an example/sample to read perf counters that I can > >> >>> >>>> > follow? > >> >>> >>>> > The code below is what I'm trying to execute. > >> >>> >>>> > > >> >>> >>>> > Thanks, > >> >>> >>>> > Riya > >> >>> >>>> > > >> >>> >>>> > # load BPF program > >> >>> >>>> > > >> >>> >>>> > bpf_text = """ > >> >>> >>>> > > >> >>> >>>> > #include <uapi/linux/ptrace.h> > >> >>> >>>> > > >> >>> >>>> > BPF_PERF_ARRAY(my_map, 32); > >> >>> >>>> > > >> >>> >>>> > int start_counting(struct pt_regs *ctx) { > >> >>> >>>> > > >> >>> >>>> > if (!PT_REGS_PARM1(ctx)) > >> >>> >>>> > > >> >>> >>>> > return 0; > >> >>> >>>> > > >> >>> >>>> > u64 count; > >> >>> >>>> > > >> >>> >>>> > u32 key = bpf_get_smp_processor_id(); > >> >>> >>>> > > >> >>> >>>> > count = bpf_perf_event_read(&my_map, key); > >> >>> >>>> > > >> >>> >>>> > bpf_trace_printk("CPU-%d %llu", key, count); > >> >>> >>>> > > >> >>> >>>> > return 0; > >> >>> >>>> > > >> >>> >>>> > } > >> >>> >>>> > > >> >>> >>>> > """ > >> >>> >>>> _______________________________________________ > >> >>> >>>> iovisor-dev mailing list > >> >>> >>>> [email protected] > >> >>> >>>> https://lists.iovisor.org/mailman/listinfo/iovisor-dev > >> >>> >>> > >> >>> >>> > >> >> > >> >> > > > > >
_______________________________________________ iovisor-dev mailing list [email protected] https://lists.iovisor.org/mailman/listinfo/iovisor-dev
