On Tue, Aug 9, 2016 at 12:05 PM, Brenden Blanco <bbla...@plumgrid.com> wrote:
> On Tue, Aug 9, 2016 at 8:54 AM, riya khanna <riyakhanna1...@gmail.com>
> 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)? Also, is it possible to handle counter overflow?
>>
>>
>> Thanks,
>> Riya
>>
>> On Fri, Jul 29, 2016 at 1:57 PM, riya khanna <riyakhanna1...@gmail.com>
>> 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 <bbla...@plumgrid.com>
>> > wrote:
>> >> On Fri, Jul 29, 2016 at 10:21 AM, riya khanna
>> >> <riyakhanna1...@gmail.com>
>> >> 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
>> >>> <riyakhanna1...@gmail.com>
>> >>> 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
>> >>> > <riyakhanna1...@gmail.com>
>> >>> > 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
>> >>> >> <bbla...@plumgrid.com>
>> >>> >> 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
>> >>> >>> <iovisor-dev@lists.iovisor.org> 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
>> >>> >>>> <riyakhanna1...@gmail.com>
>> >>> >>>> 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
>> >>> >>>> iovisor-dev@lists.iovisor.org
>> >>> >>>> https://lists.iovisor.org/mailman/listinfo/iovisor-dev
>> >>> >>>
>> >>> >>>
>> >>
>> >>
>
>
_______________________________________________
iovisor-dev mailing list
iovisor-dev@lists.iovisor.org
https://lists.iovisor.org/mailman/listinfo/iovisor-dev
