XDP hardware hints discussion mail archive
 help / color / mirror / Atom feed
From: "Song, Yoong Siang" <yoong.siang.song@intel.com>
To: John Fastabend <john.fastabend@gmail.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@intel.com>,
	"Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Richard Cochran <richardcochran@gmail.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"Jesper Dangaard Brouer" <hawk@kernel.org>,
	Stanislav Fomichev <sdf@google.com>,
	"Gomes, Vinicius" <vinicius.gomes@intel.com>,
	"Bezdeka, Florian" <florian.bezdeka@siemens.com>,
	Andrii Nakryiko <andrii@kernel.org>,
	"Eduard Zingerman" <eddyz87@gmail.com>,
	Mykola Lysenko <mykolal@fb.com>,
	"Martin KaFai Lau" <martin.lau@linux.dev>,
	Song Liu <song@kernel.org>,
	Yonghong Song <yonghong.song@linux.dev>,
	KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>, Shuah Khan <shuah@kernel.org>
Cc: "intel-wired-lan@lists.osuosl.org"
	<intel-wired-lan@lists.osuosl.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"xdp-hints@xdp-project.net" <xdp-hints@xdp-project.net>
Subject: [xdp-hints] Re: [PATCH iwl-next,v2 2/2] igc: Add Tx hardware timestamp request for AF_XDP zero-copy packet
Date: Sat, 2 Mar 2024 04:04:08 +0000	[thread overview]
Message-ID: <PH0PR11MB58305CA6B9ECA2005DC315CCD85D2@PH0PR11MB5830.namprd11.prod.outlook.com> (raw)
In-Reply-To: <65e2165a89ed0_5dcfe20823@john.notmuch>

On Saturday, March 2, 2024 1:55 AM, John Fastabend <john.fastabend@gmail.com> wrote:
>Song Yoong Siang wrote:
>> 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. Both *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().
>>
>> Co-developed-by: Lai Peter Jun Ann <jun.ann.lai@intel.com>
>> Signed-off-by: Lai Peter Jun Ann <jun.ann.lai@intel.com>
>> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
>> ---
>
>[...]
>
>>
>> +static void igc_xsk_request_timestamp(void *_priv)
>> +{
>> +	struct igc_metadata_request *meta_req = _priv;
>> +	struct igc_ring *tx_ring = meta_req->tx_ring;
>> +	struct igc_tx_timestamp_request *tstamp;
>> +	u32 tx_flags = IGC_TX_FLAGS_TSTAMP;
>> +	struct igc_adapter *adapter;
>> +	unsigned long lock_flags;
>> +	bool found = false;
>> +	int i;
>> +
>> +	if (test_bit(IGC_RING_FLAG_TX_HWTSTAMP, &tx_ring->flags)) {
>> +		adapter = netdev_priv(tx_ring->netdev);
>> +
>> +		spin_lock_irqsave(&adapter->ptp_tx_lock, lock_flags);
>> +
>> +		/* Search for available tstamp regs */
>> +		for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
>> +			tstamp = &adapter->tx_tstamp[i];
>> +
>> +			if (tstamp->skb)
>> +				continue;
>> +
>> +			found = true;
>> +			break;
>
>Not how I would have written this loop construct seems a bit odd
>to default break but it works.

Hi John,
First of all, thank you for reviewing the patch.
I agree that we can make the loop better. 
How about I change the loop to below:

for (i = 0; i < IGC_MAX_TX_TSTAMP_REGS; i++) {
	tstamp = &adapter->tx_tstamp[i];

	if (!tstamp->skb) {
		found = true;
		break;
	}
}

>
>> +		}
>> +
>> +		/* Return if no available tstamp regs */
>> +		if (!found) {
>> +			adapter->tx_hwtstamp_skipped++;
>> +			spin_unlock_irqrestore(&adapter->ptp_tx_lock,
>> +					       lock_flags);
>> +			return;
>> +		}
>
>[...]
>
>>
>> +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;
>> +		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);
>
>Just curious because I didn't find it. Fairly sure I just need to look more,
>but don't you want to still 'tstamp->skb = NULL' in this path somewhere?
>It looks like triggering the tx interrupt again with buffer_type == 0 wouldn't
>do the null.
>
>I suspect I just missed it.

Since the timestamp register will only be used by either skb or xsk,
So we make tstamp->xsk_tx_buffer and tstamp->skb as union,
Then based on tstamp->buffer_type to decide whether
tstamp->xsk_tx_buffer or tstamp->skb should be used.

My thought is, by setting tstamp->xsk_tx_buffer=NULL,
tstamp->skb will become NULL as well, and vice versa.

Thanks & Regards
Siang







  reply	other threads:[~2024-03-02  4:04 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-01 16:23 [xdp-hints] [PATCH iwl-next,v2 0/2] XDP Tx Hardware Timestamp for igc driver Song Yoong Siang
2024-03-01 16:23 ` [xdp-hints] [PATCH iwl-next,v2 1/2] selftests/bpf: xdp_hw_metadata reduce sleep interval Song Yoong Siang
2024-03-01 17:23   ` [xdp-hints] " John Fastabend
2024-03-01 18:10   ` Stanislav Fomichev
2024-03-01 16:23 ` [xdp-hints] [PATCH iwl-next,v2 2/2] igc: Add Tx hardware timestamp request for AF_XDP zero-copy packet Song Yoong Siang
2024-03-01 17:54   ` [xdp-hints] " John Fastabend
2024-03-02  4:04     ` Song, Yoong Siang [this message]
2024-03-03  1:58       ` John Fastabend
2024-03-03  7:15         ` Song, Yoong Siang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://lists.xdp-project.net/postorius/lists/xdp-hints.xdp-project.net/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=PH0PR11MB58305CA6B9ECA2005DC315CCD85D2@PH0PR11MB5830.namprd11.prod.outlook.com \
    --to=yoong.siang.song@intel.com \
    --cc=andrii@kernel.org \
    --cc=anthony.l.nguyen@intel.com \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=davem@davemloft.net \
    --cc=eddyz87@gmail.com \
    --cc=edumazet@google.com \
    --cc=florian.bezdeka@siemens.com \
    --cc=haoluo@google.com \
    --cc=hawk@kernel.org \
    --cc=intel-wired-lan@lists.osuosl.org \
    --cc=jesse.brandeburg@intel.com \
    --cc=john.fastabend@gmail.com \
    --cc=jolsa@kernel.org \
    --cc=kpsingh@kernel.org \
    --cc=kuba@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=martin.lau@linux.dev \
    --cc=mykolal@fb.com \
    --cc=netdev@vger.kernel.org \
    --cc=pabeni@redhat.com \
    --cc=richardcochran@gmail.com \
    --cc=sdf@google.com \
    --cc=shuah@kernel.org \
    --cc=song@kernel.org \
    --cc=vinicius.gomes@intel.com \
    --cc=xdp-hints@xdp-project.net \
    --cc=yonghong.song@linux.dev \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox