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Date: Tue, 26 Mar 2024 14:19:55 +0000
From: "Song, Yoong Siang" <yoong.siang.song@...el.com>
To: "Gomes, Vinicius" <vinicius.gomes@...el.com>, "Brandeburg, Jesse"
<jesse.brandeburg@...el.com>, "Nguyen, Anthony L"
<anthony.l.nguyen@...el.com>, "David S . Miller" <davem@...emloft.net>, "Eric
Dumazet" <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>, Richard Cochran <richardcochran@...il.com>, "Alexei
Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper
Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>,
Stanislav Fomichev <sdf@...gle.com>, "Bezdeka, Florian"
<florian.bezdeka@...mens.com>, Kurt Kanzenbach <kurt@...utronix.de>,
"Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>
CC: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"bpf@...r.kernel.org" <bpf@...r.kernel.org>, "xdp-hints@...-project.net"
<xdp-hints@...-project.net>
Subject: RE: [PATCH iwl-next,v4 1/1] igc: Add Tx hardware timestamp request
for AF_XDP zero-copy packet
On Tuesday, March 26, 2024 10:29 AM, Gomes, Vinicius <vinicius.gomes@...el.com> wrote:
>Song Yoong Siang <yoong.siang.song@...el.com> writes:
>
>> This patch adds support to per-packet Tx hardware timestamp request to
>> AF_XDP zero-copy packet via XDP Tx metadata framework. Please note that
>> user needs to enable Tx HW timestamp capability via igc_ioctl() with
>> SIOCSHWTSTAMP cmd before sending xsk Tx hardware timestamp request.
>>
>> Same as implementation in RX timestamp XDP hints kfunc metadata, Timer 0
>> (adjustable clock) is used in xsk Tx hardware timestamp. i225/i226 have
>> four sets of timestamping registers. *skb and *xsk_tx_buffer pointers
>> are used to indicate whether the timestamping register is already occupied.
>>
>> Furthermore, a boolean variable named xsk_pending_ts is used to hold the
>> transmit completion until the tx hardware timestamp is ready. This is
>> because, for i225/i226, the timestamp notification event comes some time
>> after the transmit completion event. The driver will retrigger hardware irq
>> to clean the packet after retrieve the tx hardware timestamp.
>>
>> Besides, xsk_meta is added into struct igc_tx_timestamp_request as a hook
>> to the metadata location of the transmit packet. When the Tx timestamp
>> interrupt is fired, the interrupt handler will copy the value of Tx hwts
>> into metadata location via xsk_tx_metadata_complete().
>>
>> This patch is tested with tools/testing/selftests/bpf/xdp_hw_metadata
>> on Intel ADL-S platform. Below are the test steps and results.
>>
>> Test Step 1: Run xdp_hw_metadata app
>> ./xdp_hw_metadata <iface> > /dev/shm/result.log
>>
>> Test Step 2: Enable Tx hardware timestamp
>> hwstamp_ctl -i <iface> -t 1 -r 1
>>
>> Test Step 3: Run ptp4l and phc2sys for time synchronization
>>
>> Test Step 4: Generate UDP packets with 1ms interval for 10s
>> trafgen --dev <iface> '{eth(da=<addr>), udp(dp=9091)}' -t 1ms -n 10000
>>
>> Test Step 5: Rerun Step 1-3 with 10s iperf3 as background traffic
>>
>> Test Step 6: Rerun Step 1-4 with 10s iperf3 as background traffic
>>
>> Based on iperf3 results below, the impact of holding tx completion to
>> throughput is not observable.
>>
>> Result of last UDP packet (no. 10000) in Step 4:
>> poll: 1 (0) skip=99 fail=0 redir=10000
>> xsk_ring_cons__peek: 1
>> 0x5640a37972d0: rx_desc[9999]->addr=f2110 addr=f2110 comp_addr=f2110 EoP
>> rx_hash: 0x2049BE1D with RSS type:0x1
>> HW RX-time: 1679819246792971268 (sec:1679819246.7930) delta to User RX-time
>sec:0.0000 (14.990 usec)
>> XDP RX-time: 1679819246792981987 (sec:1679819246.7930) delta to User RX-time
>sec:0.0000 (4.271 usec)
>> No rx_vlan_tci or rx_vlan_proto, err=-95
>> 0x5640a37972d0: ping-pong with csum=ab19 (want 315b) csum_start=34
>csum_offset=6
>> 0x5640a37972d0: complete tx idx=9999 addr=f010
>> HW TX-complete-time: 1679819246793036971 (sec:1679819246.7930) delta to
>User TX-complete-time sec:0.0001 (77.656 usec)
>> XDP RX-time: 1679819246792981987 (sec:1679819246.7930) delta to User TX-
>complete-time sec:0.0001 (132.640 usec)
>> HW RX-time: 1679819246792971268 (sec:1679819246.7930) delta to HW TX-
>complete-time sec:0.0001 (65.703 usec)
>> 0x5640a37972d0: complete rx idx=10127 addr=f2110
>>
>> Result of iperf3 without tx hwts request in step 5:
>> [ ID] Interval Transfer Bitrate Retr
>> [ 5] 0.00-10.00 sec 2.74 GBytes 2.36 Gbits/sec 0 sender
>> [ 5] 0.00-10.05 sec 2.74 GBytes 2.34 Gbits/sec receiver
>>
>> Result of iperf3 running parallel with trafgen command in step 6:
>> [ ID] Interval Transfer Bitrate Retr
>> [ 5] 0.00-10.00 sec 2.74 GBytes 2.36 Gbits/sec 0 sender
>> [ 5] 0.00-10.04 sec 2.74 GBytes 2.34 Gbits/sec receiver
>>
>> Co-developed-by: Lai Peter Jun Ann <jun.ann.lai@...el.com>
>> Signed-off-by: Lai Peter Jun Ann <jun.ann.lai@...el.com>
>> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
>> Acked-by: John Fastabend <john.fastabend@...il.com>
>> ---
>> V1:
>https://patchwork.kernel.org/project/netdevbpf/patch/20231215162158.951925-1-
>yoong.siang.song@...el.com/
>> V2:
>https://patchwork.kernel.org/project/netdevbpf/cover/20240301162348.898619-1-
>yoong.siang.song@...el.com/
>> V3:
>https://patchwork.kernel.org/project/netdevbpf/cover/20240303083225.1184165-1-
>yoong.siang.song@...el.com/
>>
>> changelog:
>> V1 -> V2
>> - In struct igc_tx_timestamp_request, keep a pointer to igc_tx_buffer,
>> instead of pointing xsk_pending_ts (Vinicius).
>> - In struct igc_tx_timestamp_request, introduce buffer_type to indicate
>> whether skb or igc_tx_buffer pointer should be use (Vinicius).
>> - In struct igc_metadata_request, remove igc_adapter pointer (Vinicius).
>> - When request tx hwts, copy the value of cmd_type, instead of using
>> pointer (Vinicius).
>> - For boolean variable, use true and false, instead of 1 and 0 (Vinicius).
>> - In igc_xsk_request_timestamp(), make an early return if none of the 4 ts
>> registers is available (Vinicius).
>> - Create helper functions to clear tx buffer and skb for tstamp (John).
>> - Perform throughput test with mix traffic (Vinicius & John).
>> V2 -> V3
>> - Improve tstamp reg searching loop for better readability (John).
>> - In igc_ptp_free_tx_buffer(), add comment to inform user that
>> tstamp->xsk_tx_buffer and tstamp->skb are in union (John).
>> V3 -> V4
>> - Add protection with xp_tx_metadata_enabled (Kurt & Maciej).
>> ---
>> ---
>> drivers/net/ethernet/intel/igc/igc.h | 71 ++++++++------
>> drivers/net/ethernet/intel/igc/igc_main.c | 113 ++++++++++++++++++++--
>> drivers/net/ethernet/intel/igc/igc_ptp.c | 51 ++++++++--
>> 3 files changed, 195 insertions(+), 40 deletions(-)
>>
>
>[...]
>
>> diff --git a/drivers/net/ethernet/intel/igc/igc_ptp.c
>b/drivers/net/ethernet/intel/igc/igc_ptp.c
>> index 885faaa7b9de..1bb026232efc 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_ptp.c
>> +++ b/drivers/net/ethernet/intel/igc/igc_ptp.c
>> @@ -11,6 +11,7 @@
>> #include <linux/ktime.h>
>> #include <linux/delay.h>
>> #include <linux/iopoll.h>
>> +#include <net/xdp_sock_drv.h>
>>
>> #define INCVALUE_MASK 0x7fffffff
>> #define ISGN 0x80000000
>> @@ -545,6 +546,30 @@ static void igc_ptp_enable_rx_timestamp(struct
>igc_adapter *adapter)
>> wr32(IGC_TSYNCRXCTL, val);
>> }
>>
>> +static void igc_ptp_free_tx_buffer(struct igc_adapter *adapter,
>> + struct igc_tx_timestamp_request *tstamp)
>> +{
>> + if (tstamp->buffer_type == IGC_TX_BUFFER_TYPE_XSK) {
>> + /* Release the transmit completion */
>> + tstamp->xsk_tx_buffer->xsk_pending_ts = false;
>> +
>> + /* Note: tstamp->skb and tstamp->xsk_tx_buffer are in union.
>> + * By setting tstamp->xsk_tx_buffer to NULL, tstamp->skb will
>> + * become NULL as well.
>> + */
>> + tstamp->xsk_tx_buffer = NULL;
>> + tstamp->buffer_type = 0;
>> +
>> + /* Trigger txrx interrupt for transmit completion */
>> + igc_xsk_wakeup(adapter->netdev, tstamp->xsk_queue_index, 0);
>> +
>> + return;
>> + }
>> +
>> + dev_kfree_skb_any(tstamp->skb);
>> + tstamp->skb = NULL;
>> +}
>> +
>> static void igc_ptp_clear_tx_tstamp(struct igc_adapter *adapter)
>> {
>> unsigned long flags;
>> @@ -555,8 +580,8 @@ static void igc_ptp_clear_tx_tstamp(struct igc_adapter
>*adapter)
>> for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
>> struct igc_tx_timestamp_request *tstamp = &adapter->tx_tstamp[i];
>>
>> - dev_kfree_skb_any(tstamp->skb);
>> - tstamp->skb = NULL;
>> + if (tstamp->skb)
>> + igc_ptp_free_tx_buffer(adapter, tstamp);
>> }
>>
>
>More a question: you are potentially triggering an interrupt from
>igc_ptp_clear_tx_tstamp() (igc_xsk_wakeup()) which can be called from
>igc_down(). So, how does it work when there's a pending timestamp and
>you remove the igc module? (example of a situation that it might be
>problematic).
Hi Vinicius,
Thanks for reviewing the patch.
There is test_bit(__IGC_DOWN, &adapter->state) checking in
igc_sxk_wakeup(). Since igc_down() will set __IGC_DOWN before
call into igc_ptp_suspend(), so I believe the checking in igc_sxk_wakeup()
should be enough to prevent the situation that you mentioned.
>
>
>Cheers,
>--
>Vinicius
Thanks & Regards
Siang
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