Re: [PATCH 0/3] testpmd support stop specify lcore

[fengchengwen <fengchengwen@huawei.com>]

On 11/5/2025 8:21 AM, Stephen Hemminger wrote:
> On Tue, 4 Nov 2025 12:09:13 +0800
> Chengwen Feng <fengchengwen@huawei.com> wrote:
> 
>> This patch support stop specify lcore for testpmd, and also include
>> two bugfix which found when test DCB function.
>>
>> Chengwen Feng (3):
>>   app/testpmd: fix invalid txp when setup DCB forward
>>   app/testpmd: fix wrong Rx queues when setup DCB forward
>>   app/testpmd: support stop specify lcore
>>
>>  app/test-pmd/cmdline.c                      | 63 +++++++++++++++++++++
>>  app/test-pmd/config.c                       |  9 +--
>>  doc/guides/testpmd_app_ug/testpmd_funcs.rst |  7 +++
>>  3 files changed, 73 insertions(+), 6 deletions(-)
>>
> 
> If there is a stop lcore, why is there not a command to restart the lcore?

The restart lcore is more complex which include data prepare (init).

But I think could impl such pause / restart function by config fc->stopped a special value:

Current:
	run_pkt_fwd_on_lcore(struct fwd_lcore *fc, packet_fwd_t pkt_fwd)
	{
		do {
			forwarding logic
		} while(!fc->stopped);
	}

We could adjust the logic to support pause / restart function:
	run_pkt_fwd_on_lcore(struct fwd_lcore *fc, packet_fwd_t pkt_fwd)
	{
	_restart:
		do {
			forwarding logic
		} while(!fc->stopped);
 		while (fc->stopped == 2) {
			nop
		}
		if (fc->stopped == 1)
			return;
		if (fc->stopped == 0)
			// means restart
			goto _restart;
	}
So we could configure fc->stopped = 2 to pause forwarding, and config it to 0 to restart forwarding.

> Looks like this just an optimization for DCB.

Yes, mainly for test the Tx direction's DCB function.

> Could it be handled better by having testpmd not spawn lcores that
> have no queues? 

The lcore spawned by testpmd always has queues. In this patchset, we just stop some queue's forwarding.

>