netdev - Re: [PATCH perf/core REBASE 2/5] samples/bpf: Switch over to libbpf

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Date:   Fri, 16 Dec 2016 12:42:42 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Joe Stringer <joe@....org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, Wang Nan <wangnan0@...wei.com>,
        ast@...com, Daniel Borkmann <daniel@...earbox.net>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH perf/core REBASE 2/5] samples/bpf: Switch over to libbpf

Em Thu, Dec 15, 2016 at 05:48:31PM -0800, Joe Stringer escreveu:
> On 15 December 2016 at 14:00, Joe Stringer <joe@....org> wrote:
> > On 15 December 2016 at 10:34, Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> >> Em Thu, Dec 15, 2016 at 03:29:18PM -0300, Arnaldo Carvalho de Melo escreveu:
> >>> Em Thu, Dec 15, 2016 at 12:50:22PM -0300, Arnaldo Carvalho de Melo escreveu:
> >>> > Em Wed, Dec 14, 2016 at 02:43:39PM -0800, Joe Stringer escreveu:
> >>> > > Now that libbpf under tools/lib/bpf/* is synced with the version from
> >>> > > samples/bpf, we can get rid most of the libbpf library here.
> >>> > >
> >>> > > Signed-off-by: Joe Stringer <joe@....org>
> >>> > > Cc: Alexei Starovoitov <ast@...com>
> >>> > > Cc: Daniel Borkmann <daniel@...earbox.net>
> >>> > > Cc: Wang Nan <wangnan0@...wei.com>
> >>> > > Link: http://lkml.kernel.org/r/20161209024620.31660-6-joe@ovn.org
> >>> > > [ Use -I$(srctree)/tools/lib/ to support out of source code tree builds, as noticed by Wang Nan ]
> >>>
> >>> So, the above comment no longer applied to this adjusted patch from you,
> >>> as you removed one hunk too much, that, after applied, gets samples/bpf/
> >>> to build successfully:
> >>>
> >>> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> >>> index add514e2984a..81b0ef2f7994 100644
> >>> --- a/samples/bpf/Makefile
> >>> +++ b/samples/bpf/Makefile
> >>> @@ -107,6 +107,7 @@ always += lwt_len_hist_kern.o
> >>>  always += xdp_tx_iptunnel_kern.o
> >>>
> >>>  HOSTCFLAGS += -I$(objtree)/usr/include
> >>> +HOSTCFLAGS += -I$(srctree)/tools/lib/
> >>>  HOSTCFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
> >>>
> >>>  HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
> >>>
> >>> ---------------------
> >>>
> >>> I added it, continuing...
> >>
> >> But then, when I tried to run offwaketime with it, it fails:
> >>
> >> [root@...et bpf]# ./offwaketime  ls
> >> bpf_load_program() err=22
> >> BPF_LDX uses reserved fields
> >> bpf_load_program() err=22
> >> BPF_LDX uses reserved fields
> >> [root@...et bpf]#
> >>
> >> If I remove this patch and try again, it works:
> >>
> >> [root@...et bpf]# ./offwaketime | head -4
> >> swapper/1;start_secondary;cpu_startup_entry;schedule_preempt_disabled;schedule;__schedule;-;---;; 46
> >> chrome;return_from_SYSCALL_64;do_syscall_64;exit_to_usermode_loop;schedule;__schedule;-;try_to_wake_up;do_futex;sys_futex;do_syscall_64;return_from_SYSCALL_64;;Chrome_ChildIOT 1
> >> firefox;entry_SYSCALL_64_fastpath;sys_poll;do_sys_poll;poll_schedule_timeout;schedule_hrtimeout_range;schedule_hrtimeout_range_clock;schedule;__schedule;-;try_to_wake_up;pollwake;__wake_up_common;__wake_up_sync_key;pipe_write;__vfs_write;vfs_write;sys_write;entry_SYSCALL_64_fastpath;;Timer 3
> >> dockerd-current;entry_SYSCALL_64_fastpath;sys_select;core_sys_select;do_select;poll_schedule_timeout;schedule_hrtimeout_range;schedule_hrtimeout_range_clock;schedule;__schedule;-;try_to_wake_up;futex_wake;do_futex;sys_futex;entry_SYSCALL_64_fastpath;;dockerd-current 2
> >> [root@...et bpf]#
> >>
> >>
> >> So, I'm stopping here so that I can push what I have to Ingo, then I'll get
> >> back to this, hopefully by then you beat me and I have just to retest 8-)
> >
> > OK, thanks for the report. Looks like there was another difference
> > between the two libbpfs - one used total program size for its
> > load_program API; the actual kernel API uses instruction count. This
> > incremental should do the trick:
> >
> > https://github.com/joestringer/linux/commit/6ff7726f20077bed66fb725f5189c13690154b6a
> 
> The full branch with this change (fast-forward from your tmp branch)
> is available here:
> https://github.com/joestringer/linux/tree/submit/libbpf_samples_v5

Can you please repost the patches you changed, and just those, sometimes
I'm with limited net connectivity, so not having to go use the github
interface, figure out how to download the patches, etc, is a win.

- Arnaldo
 
> I tried running every selftest and BPF sample I could get my hands on;
> there's one or two that I couldn't run, but seemed more to do with my
> versions of TC/iproute and kernel config rather than libbpf changes.
> Let me know if you see any further trouble.