From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Alexei Starovoitov <ast@fb.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Jann Horn <jannh@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexei Starovoitov <ast@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
"jakub.kicinski@netronome.com" <jakub.kicinski@netronome.com>,
Network Development <netdev@vger.kernel.org>,
Kernel Team <Kernel-team@fb.com>, Ingo Molnar <mingo@redhat.com>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH v4 bpf-next 1/9] bpf: introduce bpf_spin_lock
Date: Thu, 24 Jan 2019 20:31:58 -0800 [thread overview]
Message-ID: <20190125043158.GB4240@linux.ibm.com> (raw)
In-Reply-To: <150dc5d3-21c3-bbb6-6e5b-2ab8ab0e3f38@fb.com>
On Fri, Jan 25, 2019 at 04:27:02AM +0000, Alexei Starovoitov wrote:
> On 1/24/19 6:38 PM, Alexei Starovoitov wrote:
> >> For programs created with CAP_SYS_ADMIN,
> >> things get more tricky because you can create your own functions and
> >> call them repeatedly; I'm not sure whether the pessimal runtime there
> >> becomes exponential, or whether there is some check that catches this.
> > I think you're referring to bpf-to-bpf calls.
> > The limit it still the same. 4k per program including all calls.
> > tail calls are not allowed when bpf-to-bpf is used. So no 32 multiplier.
>
> Jann,
>
> I think you meant
> main:
> call A
> call A
> call A
> exit
> A:
> call B
> call B
> call B
> exit
> B:
> call C
> ...
>
> scenario when everything fits into 4k?
> Would be great if you can construct such test while we're fixing
> the rest of the issues brought up in this thread.
> It will definitely be no more than BPF_COMPLEXITY_LIMIT_INSNS
> which is 128k, but I wonder what will be the actual number of
> executed insns.
> I think such clever constructed sequence can actually
> hit 128k executed too.
> It would be awesome test to add to test_verifier.c
> We have some of such pushing-the-boundary tests in lib/test_bpf.c
> that are generated in assembler.
> The longest takes 23853 nanoseconds, but clever bpf2bpf call hack
> like above with map_update call in the leaf function should
> certainly take much longer.
> I accept Paul's challenge to try to get such fancy bpf prog
> to take 100 millseconds :)
Fair enough! But once you meet my challenge, the RCU CPU stall warning
code will challenge you to hit 21 seconds (or only three seconds given
an appropriately configured kernel). ;-)
Thanx, Paul
next prev parent reply other threads:[~2019-01-25 4:32 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-24 4:13 [PATCH v4 bpf-next 0/9] introduce bpf_spin_lock Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 1/9] bpf: " Alexei Starovoitov
2019-01-24 18:01 ` Peter Zijlstra
2019-01-24 18:56 ` Peter Zijlstra
2019-01-24 23:42 ` Paul E. McKenney
2019-01-25 0:05 ` Alexei Starovoitov
2019-01-25 1:22 ` Paul E. McKenney
2019-01-25 1:46 ` Jann Horn
2019-01-25 2:38 ` Alexei Starovoitov
2019-01-25 4:27 ` Alexei Starovoitov
2019-01-25 4:31 ` Paul E. McKenney [this message]
2019-01-25 4:47 ` Alexei Starovoitov
2019-01-25 16:02 ` Paul E. McKenney
2019-01-25 4:11 ` Paul E. McKenney
2019-01-25 16:18 ` Jann Horn
2019-01-25 22:51 ` Paul E. McKenney
2019-01-25 23:44 ` Alexei Starovoitov
2019-01-26 0:43 ` Jann Horn
2019-01-26 0:59 ` Jann Horn
2019-01-24 23:58 ` Alexei Starovoitov
2019-01-25 0:18 ` Jann Horn
2019-01-25 2:49 ` Alexei Starovoitov
2019-01-25 2:29 ` Eric Dumazet
2019-01-25 2:34 ` Alexei Starovoitov
2019-01-25 2:44 ` Eric Dumazet
2019-01-25 2:57 ` Alexei Starovoitov
2019-01-25 8:38 ` Peter Zijlstra
2019-01-25 9:10 ` Peter Zijlstra
2019-01-25 23:42 ` Alexei Starovoitov
2019-01-28 8:24 ` Peter Zijlstra
2019-01-28 8:31 ` Peter Zijlstra
2019-01-28 8:35 ` Peter Zijlstra
2019-01-28 20:49 ` Alexei Starovoitov
2019-01-28 8:43 ` Peter Zijlstra
2019-01-28 21:37 ` Alexei Starovoitov
2019-01-29 8:59 ` Peter Zijlstra
2019-01-30 2:20 ` Alexei Starovoitov
2019-01-25 9:59 ` Peter Zijlstra
2019-01-25 10:09 ` Peter Zijlstra
2019-01-25 10:23 ` Peter Zijlstra
2019-01-26 0:17 ` bpf memory model. Was: " Alexei Starovoitov
2019-01-28 9:24 ` Peter Zijlstra
2019-01-28 21:56 ` Alexei Starovoitov
2019-01-29 9:16 ` Peter Zijlstra
2019-01-30 2:32 ` Alexei Starovoitov
2019-01-30 8:58 ` Peter Zijlstra
2019-01-30 19:36 ` Alexei Starovoitov
2019-01-30 18:11 ` Will Deacon
2019-01-30 18:36 ` Paul E. McKenney
2019-01-30 19:51 ` Alexei Starovoitov
2019-01-30 21:05 ` Paul E. McKenney
2019-01-30 22:57 ` Alexei Starovoitov
2019-01-31 14:01 ` Paul E. McKenney
2019-01-31 18:47 ` Alexei Starovoitov
2019-02-01 14:05 ` Paul E. McKenney
2019-01-30 19:50 ` Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 2/9] bpf: add support for bpf_spin_lock to cgroup local storage Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 3/9] tools/bpf: sync include/uapi/linux/bpf.h Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 4/9] selftests/bpf: add bpf_spin_lock tests Alexei Starovoitov
2019-01-24 4:13 ` [PATCH v4 bpf-next 5/9] selftests/bpf: add bpf_spin_lock C test Alexei Starovoitov
2019-01-24 4:14 ` [PATCH v4 bpf-next 6/9] bpf: introduce BPF_F_LOCK flag Alexei Starovoitov
2019-01-24 4:14 ` [PATCH v4 bpf-next 7/9] tools/bpf: sync uapi/bpf.h Alexei Starovoitov
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