From: Neal Cardwell <ncardwell@google.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Martin KaFai Lau <kafai@fb.com>,
bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
David Miller <davem@davemloft.net>,
Kernel Team <kernel-team@fb.com>, Netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH bpf-next 09/13] bpf: Add BPF_FUNC_jiffies
Date: Sat, 14 Dec 2019 14:25:14 -0500 [thread overview]
Message-ID: <CADVnQy=soQ8KhuUWEQj0n2ge3a43OSgAKS95bmBtp090jqbM_w@mail.gmail.com> (raw)
In-Reply-To: <b321412c-1b42-45a9-4dc6-cc268b55cd0d@gmail.com>
On Fri, Dec 13, 2019 at 9:00 PM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
>
>
> On 12/13/19 4:47 PM, Martin KaFai Lau wrote:
> > This patch adds a helper to handle jiffies. Some of the
> > tcp_sock's timing is stored in jiffies. Although things
> > could be deduced by CONFIG_HZ, having an easy way to get
> > jiffies will make the later bpf-tcp-cc implementation easier.
> >
>
> ...
>
> > +
> > +BPF_CALL_2(bpf_jiffies, u64, in, u64, flags)
> > +{
> > + if (!flags)
> > + return get_jiffies_64();
> > +
> > + if (flags & BPF_F_NS_TO_JIFFIES) {
> > + return nsecs_to_jiffies(in);
> > + } else if (flags & BPF_F_JIFFIES_TO_NS) {
> > + if (!in)
> > + in = get_jiffies_64();
> > + return jiffies_to_nsecs(in);
> > + }
> > +
> > + return 0;
> > +}
>
> This looks a bit convoluted :)
>
> Note that we could possibly change net/ipv4/tcp_cubic.c to no longer use jiffies at all.
>
> We have in tp->tcp_mstamp an accurate timestamp (in usec) that can be converted to ms.
If the jiffies functionality stays, how about 3 simple functions that
correspond to the underlying C functions, perhaps something like:
bpf_nsecs_to_jiffies(nsecs)
bpf_jiffies_to_nsecs(jiffies)
bpf_get_jiffies_64()
Separate functions might be easier to read/maintain (and may even be
faster, given the corresponding reduction in branches).
neal
next prev parent reply other threads:[~2019-12-14 19:25 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-14 0:47 [PATCH bpf-next 00/13] Introduce BPF STRUCT_OPS Martin KaFai Lau
2019-12-14 0:47 ` [PATCH bpf-next 01/13] bpf: Save PTR_TO_BTF_ID register state when spilling to stack Martin KaFai Lau
2019-12-16 19:48 ` Yonghong Song
2019-12-14 0:47 ` [PATCH bpf-next 02/13] bpf: Avoid storing modifier to info->btf_id Martin KaFai Lau
2019-12-16 21:34 ` Yonghong Song
2019-12-14 0:47 ` [PATCH bpf-next 03/13] bpf: Add enum support to btf_ctx_access() Martin KaFai Lau
2019-12-16 21:36 ` Yonghong Song
2019-12-14 0:47 ` [PATCH bpf-next 04/13] bpf: Support bitfield read access in btf_struct_access Martin KaFai Lau
2019-12-16 22:05 ` Yonghong Song
2019-12-14 0:47 ` [PATCH bpf-next 05/13] bpf: Introduce BPF_PROG_TYPE_STRUCT_OPS Martin KaFai Lau
2019-12-17 6:14 ` Yonghong Song
2019-12-18 16:41 ` Martin Lau
2019-12-14 0:47 ` [PATCH bpf-next 06/13] bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS Martin KaFai Lau
2019-12-17 7:48 ` [Potential Spoof] " Yonghong Song
2019-12-20 7:22 ` Martin Lau
2019-12-20 16:52 ` Martin Lau
2019-12-20 18:41 ` Andrii Nakryiko
2019-12-14 0:47 ` [PATCH bpf-next 07/13] bpf: tcp: Support tcp_congestion_ops in bpf Martin KaFai Lau
2019-12-17 17:36 ` Yonghong Song
2019-12-14 0:47 ` [PATCH bpf-next 08/13] bpf: Add BPF_FUNC_tcp_send_ack helper Martin KaFai Lau
2019-12-17 17:41 ` Yonghong Song
2019-12-14 0:47 ` [PATCH bpf-next 09/13] bpf: Add BPF_FUNC_jiffies Martin KaFai Lau
2019-12-14 1:59 ` Eric Dumazet
2019-12-14 19:25 ` Neal Cardwell [this message]
2019-12-16 19:30 ` Martin Lau
2019-12-17 8:26 ` Jakub Sitnicki
2019-12-17 18:22 ` Martin Lau
2019-12-17 21:04 ` Eric Dumazet
2019-12-18 9:03 ` Jakub Sitnicki
2019-12-16 19:14 ` Martin Lau
2019-12-16 19:33 ` Eric Dumazet
2019-12-16 21:17 ` Martin Lau
2019-12-16 23:08 ` Alexei Starovoitov
2019-12-17 0:34 ` Eric Dumazet
2019-12-14 0:48 ` [PATCH bpf-next 10/13] bpf: Synch uapi bpf.h to tools/ Martin KaFai Lau
2019-12-14 0:48 ` [PATCH bpf-next 11/13] bpf: libbpf: Add STRUCT_OPS support Martin KaFai Lau
2019-12-18 3:07 ` Andrii Nakryiko
2019-12-18 7:03 ` Martin Lau
2019-12-18 7:20 ` Martin Lau
2019-12-18 16:36 ` Andrii Nakryiko
2019-12-18 16:34 ` Andrii Nakryiko
2019-12-18 17:33 ` Martin Lau
2019-12-18 18:14 ` Andrii Nakryiko
2019-12-18 20:19 ` Martin Lau
2019-12-19 8:53 ` Toke Høiland-Jørgensen
2019-12-19 20:49 ` Andrii Nakryiko
2019-12-20 10:16 ` Toke Høiland-Jørgensen
2019-12-20 17:34 ` Andrii Nakryiko
2019-12-14 0:48 ` [PATCH bpf-next 12/13] bpf: Add bpf_dctcp example Martin KaFai Lau
2019-12-14 0:48 ` [PATCH bpf-next 13/13] bpf: Add bpf_cubic example Martin KaFai Lau
2019-12-14 2:26 ` [PATCH bpf-next 00/13] Introduce BPF STRUCT_OPS Eric Dumazet
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