From: "Abhishek Chauhan (ABC)" <quic_abchauha@quicinc.com>
To: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Andrew Halaney <ahalaney@redhat.com>,
"Martin KaFai Lau" <martin.lau@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>
Cc: <kernel@quicinc.com>
Subject: Re: [RFC PATCH bpf-next v4 1/2] net: Rename mono_delivery_time to tstamp_type for scalabilty
Date: Thu, 18 Apr 2024 13:38:03 -0700 [thread overview]
Message-ID: <d25533d6-5d09-4c9f-8801-54ac35db98ed@quicinc.com> (raw)
In-Reply-To: <66217e7ccb46b_f9d5d294b0@willemb.c.googlers.com.notmuch>
On 4/18/2024 1:11 PM, Willem de Bruijn wrote:
> Abhishek Chauhan (ABC) wrote:
>>
>>
>> On 4/18/2024 11:47 AM, Willem de Bruijn wrote:
>>> Abhishek Chauhan wrote:
>>>> mono_delivery_time was added to check if skb->tstamp has delivery
>>>> time in mono clock base (i.e. EDT) otherwise skb->tstamp has
>>>> timestamp in ingress and delivery_time at egress.
>>>>
>>>> Renaming the bitfield from mono_delivery_time to tstamp_type is for
>>>> extensibilty for other timestamps such as userspace timestamp
>>>> (i.e. SO_TXTIME) set via sock opts.
>>>>
>>>> As we are renaming the mono_delivery_time to tstamp_type, it makes
>>>> sense to start assigning tstamp_type based on enum defined
>>>> in this commit.
>>>>
>>>> Earlier we used bool arg flag to check if the tstamp is mono in
>>>> function skb_set_delivery_time, Now the signature of the functions
>>>> accepts tstamp_type to distinguish between mono and real time.
>>>>
>>>> In future tstamp_type:1 can be extended to support userspace timestamp
>>>> by increasing the bitfield.
>>>>
>>>> Link: https://lore.kernel.org/netdev/bc037db4-58bb-4861-ac31-a361a93841d3@linux.dev/
>>>> Signed-off-by: Abhishek Chauhan <quic_abchauha@quicinc.com>
>>>
>>>> +/**
>>>> + * tstamp_type:1 can take 2 values each
>>>> + * represented by time base in skb
>>>> + * 0x0 => real timestamp_type
>>>> + * 0x1 => mono timestamp_type
>>>> + */
>>>> +enum skb_tstamp_type {
>>>> + SKB_CLOCK_REAL, /* Time base is skb is REALTIME */
>>>> + SKB_CLOCK_MONO, /* Time base is skb is MONOTONIC */
>>>> +};
>>>> +
>>>
>>> Can drop the comments. These names are self documenting.
>>
>> Noted! . I will take care of this
>>>
>>>> /**
>>>> * DOC: Basic sk_buff geometry
>>>> *
>>>> @@ -819,7 +830,7 @@ typedef unsigned char *sk_buff_data_t;
>>>> * @dst_pending_confirm: need to confirm neighbour
>>>> * @decrypted: Decrypted SKB
>>>> * @slow_gro: state present at GRO time, slower prepare step required
>>>> - * @mono_delivery_time: When set, skb->tstamp has the
>>>> + * @tstamp_type: When set, skb->tstamp has the
>>>> * delivery_time in mono clock base (i.e. EDT). Otherwise, the
>>>> * skb->tstamp has the (rcv) timestamp at ingress and
>>>> * delivery_time at egress.
>>>
>>> Is this still correct? I think all egress does now annotate correctly
>>> as SKB_CLOCK_MONO. So when not set it always is SKB_CLOCK_REAL.
>>>
>> That is correct.
>>
>>>> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
>>>> index 61119d42b0fd..a062f88c47c3 100644
>>>> --- a/net/ipv4/tcp_output.c
>>>> +++ b/net/ipv4/tcp_output.c
>>>> @@ -1300,7 +1300,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
>>>> tp = tcp_sk(sk);
>>>> prior_wstamp = tp->tcp_wstamp_ns;
>>>> tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache);
>>>> - skb_set_delivery_time(skb, tp->tcp_wstamp_ns, true);
>>>> + skb_set_delivery_time(skb, tp->tcp_wstamp_ns, CLOCK_MONOTONIC);
>>>
>>> Multiple references to CLOCK_MONOTONIC left
>>>
>> I think i took care of all the references. Apologies if i didn't understand your comment here.
>
> On closer read, there is a type issue here.
>
> skb_set_delivery_time takes a u8 tstamp_type. But it is often passed
> a clockid_t, and that is also what the switch expects.
>
> But it does also get called with a tstamp_type in code like the
> following:
>
> + u8 tstamp_type = skb->tstamp_type;
> unsigned int hlen, ll_rs, mtu;
> ktime_t tstamp = skb->tstamp;
> struct ip_frag_state state;
> @@ -82,7 +82,7 @@ static int nf_br_ip_fragment(struct net *net, struct sock *sk,
> if (iter.frag)
> ip_fraglist_prepare(skb, &iter);
>
> - skb_set_delivery_time(skb, tstamp, mono_delivery_time);
> + skb_set_delivery_time(skb, tstamp, tstamp_type);
>
> So maybe we need two variants, one that takes a tstamp_type and one
> that tames a clockid_t?
>
> The first can be simple, not switch needed. Just apply the two stores.
I agree to what you are saying but clockid_t => points to int itself.
For example :-
void qdisc_watchdog_init_clockid(struct qdisc_watchdog *wd, struct Qdisc *qdisc,
clockid_t clockid)
qdisc_watchdog_init_clockid(wd, qdisc, CLOCK_MONOTONIC); => sch_api.c
qdisc_watchdog_init_clockid(&q->watchdog, sch, q->clockid); =>sch_etf.c (q->clockid is int)
But i can change it to two new APIs one which accepts only clock_id (with switch) and other accepts u8 to directly store whatever is given.
next prev parent reply other threads:[~2024-04-18 20:38 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 0:43 [RFC PATCH bpf-next v4 0/2] Replace mono_delivery_time with tstamp_type Abhishek Chauhan
2024-04-18 0:43 ` [RFC PATCH bpf-next v4 1/2] net: Rename mono_delivery_time to tstamp_type for scalabilty Abhishek Chauhan
2024-04-18 18:47 ` Willem de Bruijn
2024-04-18 19:58 ` Abhishek Chauhan (ABC)
2024-04-18 20:11 ` Willem de Bruijn
2024-04-18 20:38 ` Abhishek Chauhan (ABC) [this message]
2024-04-18 20:49 ` Willem de Bruijn
2024-04-18 20:51 ` Abhishek Chauhan (ABC)
2024-04-18 0:43 ` [RFC PATCH bpf-next v4 2/2] net: Add additional bit to support clockid_t timestamp type Abhishek Chauhan
2024-04-18 19:06 ` Willem de Bruijn
2024-04-18 20:10 ` Abhishek Chauhan (ABC)
2024-04-18 21:57 ` Martin KaFai Lau
2024-04-19 0:30 ` Abhishek Chauhan (ABC)
2024-04-20 1:13 ` Abhishek Chauhan (ABC)
2024-04-22 18:46 ` Martin KaFai Lau
2024-04-24 18:03 ` Abhishek Chauhan (ABC)
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