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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Lorenz Bauer <lmb@cloudflare.com>,
	Network Development <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>, Kernel Team <kernel-team@fb.com>
Subject: Re: [RFC PATCH bpf-next] bpf: Introduce bpf_timer
Date: Mon, 24 May 2021 20:39:46 +0200	[thread overview]
Message-ID: <87cztgyo0d.fsf@toke.dk> (raw)
In-Reply-To: <CAADnVQL8qw4OYQp+ozJpgPnimNYV7PtShZ-4tqdY7fTBhHf2ww@mail.gmail.com>

Alexei Starovoitov <alexei.starovoitov@gmail.com> writes:

> On Sun, May 23, 2021 at 8:58 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
>>
>> On Sun, May 23, 2021 at 4:48 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>> >
>> > Still wrapping my head around this, but one thing immediately sprang to
>> > mind:
>> >
>> > > + * long bpf_timer_mod(struct bpf_timer *timer, u64 msecs)
>> > > + *   Description
>> > > + *           Set the timer expiration N msecs from the current time.
>> > > + *   Return
>> > > + *           zero
>> >
>> > Could we make this use nanoseconds (and wire it up to hrtimers) instead?
>> > I would like to eventually be able to use this for pacing out network
>> > packets, and msec precision is way too coarse for that...
>>
>> msecs are used to avoid exposing jiffies to bpf prog, since msec_to_jiffies
>> isn't trivial to do in the bpf prog unlike the kernel.
>> hrtimer would be great to support as well.
>> It could be implemented via flags (which are currently zero only)
>> but probably not as a full replacement for jiffies based timers.
>> Like array vs hash. bpf_timer can support both.
>
> After reading the hrtimer code I might take the above statement back...
> hrtimer looks strictly better than timerwheel and jiffies.
> It scales well and there are no concerns with overload,
> since sys_nanonsleep and tcp are heavy users.
> So I'm thinking to drop jiffies approach and do hrtimer only.
> wdyt?

Oops, sorry, crossed streams, didn't see this before sending my other
reply. Yeah, hrtimers only SGTM :)

-Toke


  reply	other threads:[~2021-05-24 18:39 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-20 18:55 [RFC PATCH bpf-next] bpf: Introduce bpf_timer Alexei Starovoitov
2021-05-21 14:38 ` Alexei Starovoitov
2021-05-21 21:37 ` Cong Wang
2021-05-23 16:01   ` Alexei Starovoitov
2021-05-24  8:45     ` Lorenz Bauer
2021-05-25  3:16     ` Cong Wang
2021-05-25  4:59       ` Cong Wang
2021-05-25 18:21         ` Alexei Starovoitov
2021-05-25 19:35           ` Jamal Hadi Salim
2021-05-25 19:57             ` Alexei Starovoitov
2021-05-25 21:09               ` Jamal Hadi Salim
2021-05-25 22:08                 ` Alexei Starovoitov
2021-05-26 15:34                   ` Jamal Hadi Salim
2021-05-26 16:58                     ` Alexei Starovoitov
2021-05-26 18:25                       ` Jamal Hadi Salim
2021-05-30  6:36           ` Cong Wang
2021-06-02  2:00             ` Alexei Starovoitov
2021-06-02  8:48               ` Toke Høiland-Jørgensen
2021-06-02 17:54                 ` Martin KaFai Lau
2021-06-02 18:13                   ` Kumar Kartikeya Dwivedi
2021-06-02 18:26                     ` Alexei Starovoitov
2021-06-02 18:30                       ` Kumar Kartikeya Dwivedi
2021-06-02 18:46                     ` John Fastabend
2021-05-23 11:48 ` Toke Høiland-Jørgensen
2021-05-23 15:58   ` Alexei Starovoitov
2021-05-24  8:42     ` Lorenz Bauer
2021-05-24 14:48       ` Alexei Starovoitov
2021-05-24 17:33     ` Alexei Starovoitov
2021-05-24 18:39       ` Toke Høiland-Jørgensen [this message]
2021-05-24 18:38     ` Toke Høiland-Jørgensen
2021-05-24 11:49 ` Lorenz Bauer
2021-05-24 14:56   ` Alexei Starovoitov
2021-05-24 19:13     ` Andrii Nakryiko
2021-05-25  5:22       ` Cong Wang
2021-05-25 19:47         ` Andrii Nakryiko
  -- strict thread matches above, loose matches on Subject: below --
2021-04-01  4:26 [RFC Patch bpf-next] bpf: introduce bpf timer Cong Wang
2021-04-01  6:38 ` Song Liu
2021-04-01 17:28   ` Cong Wang
2021-04-01 20:17     ` Song Liu
2021-04-02 17:34       ` Cong Wang
2021-04-02 17:57         ` Song Liu
2021-04-02 19:08           ` Cong Wang
2021-04-02 19:43             ` Song Liu
2021-04-02 20:57               ` Cong Wang
2021-04-02 23:31                 ` Song Liu
2021-04-05 23:49                   ` Cong Wang
2021-04-06  1:07                     ` Song Liu
2021-04-06  1:24                       ` Cong Wang
2021-04-06  6:17                         ` Song Liu
2021-04-06 16:48                           ` Cong Wang
2021-04-06 23:36                             ` Song Liu
2021-04-08 22:45                               ` Cong Wang
2021-04-02 19:28 ` Alexei Starovoitov
2021-04-02 21:24   ` Cong Wang
2021-04-02 23:45     ` Alexei Starovoitov
2021-04-06  0:36       ` Cong Wang
2021-04-12 23:01         ` Alexei Starovoitov
2021-04-15  4:02           ` Cong Wang
2021-04-15  4:25             ` Alexei Starovoitov
2021-04-15 15:51               ` Cong Wang
2021-04-26 23:00               ` Cong Wang
2021-04-26 23:05                 ` Alexei Starovoitov
2021-04-26 23:37                   ` Cong Wang
2021-04-27  2:01                     ` Alexei Starovoitov
2021-04-27 11:52                       ` Jamal Hadi Salim
2021-04-27 16:36                       ` Cong Wang
2021-04-27 18:33                         ` Alexei Starovoitov
2021-05-09  5:37                           ` Cong Wang
2021-05-10 20:55                             ` Jamal Hadi Salim
2021-05-11 21:29                               ` Cong Wang
2021-05-12 22:56                                 ` Jamal Hadi Salim
2021-05-11  5:05                             ` Joe Stringer
2021-05-11 21:08                               ` Cong Wang
2021-05-12 22:43                               ` Jamal Hadi Salim
2021-05-13 18:45                                 ` Jamal Hadi Salim
2021-05-14  2:53                                   ` Cong Wang
2021-08-11 21:03                                     ` Joe Stringer

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