linux-kernel - Re: [PATCH v4] scsi: ufs: core: Add trace event for MCQ

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Date:   Thu, 9 Mar 2023 10:44:17 +0800
From:   Ziqi Chen <quic_ziqichen@...cinc.com>
To:     Bart Van Assche <bvanassche@....org>, <quic_asutoshd@...cinc.com>,
        <quic_cang@...cinc.com>, <mani@...nel.org>,
        <stanley.chu@...iatek.com>, <adrian.hunter@...el.com>,
        <beanhuo@...ron.com>, <avri.altman@....com>,
        <junwoo80.lee@...sung.com>, <martin.petersen@...cle.com>
CC:     <linux-scsi@...r.kernel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:TRACING" <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] scsi: ufs: core: Add trace event for MCQ



On 3/7/2023 11:47 PM, Bart Van Assche wrote:
> On 3/6/23 21:53, Ziqi Chen wrote:
>> You are right,  users may hate it if the trace events for legacy mode 
>> and MCQ mode are different. But if I merge them into one event, it 
>> will print much invalid information as we can not add if-else into 
>> TP_printk().
>>
>> (For example:  in SDB legacy mode, you can see such invalid prints " 
>> hqid = 0 , sqt= 0, cqh=0, cqt = 0")
>>
>> Users may hate these invalid information.
>>
>> Anyway, I have made new version that merge 2 mode into one event, but 
>> are you sure we really need to use this way? if yes , I can push new 
>> version here.
>>
>> Or, could you give some suggestions if you have better way.
>>
>> Below is a piece of new version code , you can preview.
>>
>>      TP_fast_assign(
>>          __assign_str(dev_name, dev_name);
>>          __entry->str_t = str_t;
>>          __entry->tag = tag;
>>          __entry->doorbell = doorbell;
>>          __entry->hwq_id = hwq? hwq->id: 0;
>>          __entry->sq_tail = hwq? hwq->sq_tail_slot: 0;
>>          __entry->cq_head = hwq? hwq->cq_head_slot: 0;
>>          __entry->cq_tail = hwq? hwq->cq_tail_slot: 0;
>>          __entry->transfer_len = transfer_len;
>>          __entry->lba = lba;
>>          __entry->intr = intr;
>>          __entry->opcode = opcode;
>>          __entry->group_id = group_id;
>>      ),
>>
>>      TP_printk(
>>          "%s: %s: tag: %u, DB: 0x%x, size: %d, IS: %u, LBA: %llu, 
>> opcode: 0x%x (%s),"
>>          "group_id: 0x%x, hqid: %d, sqt: %d, cqh: %d, cqt: %d",
>>          show_ufs_cmd_trace_str(__entry->str_t), __get_str(dev_name), 
>> __entry->tag,
>>          __entry->doorbell, __entry->transfer_len, __entry->intr, 
>> __entry->lba,
>>          (u32)__entry->opcode, str_opcode(__entry->opcode), 
>> (u32)__entry->group_id,
>>          __entry->hwq_id,__entry->sq_tail, __entry->cq_head, 
>> __entry->cq_tail
>>      )
> 
> Hi Ziqi,
> 
> Please reply below the original e-mail instead of above. This is 
> expected on Linux kernel mailing lists.
> 
> Regarding your question: I propose to leave out the sq_tail, cq_head and 
> cq_tail information. That information may be useful for hardware 
> developers but is not useful for other users of the Linux kernel. So the 
> only piece of information that is left that is MCQ-specific is the 
> hardware queue index. I expect that users will be fine to see that 
> information in trace events.
> 
> How about reporting hardware queue index -1 for legacy mode instead of 
> 0? That will allow users to tell the difference between legacy mode and 
> MCQ mode from the trace events.
> 
> Thanks,
> 
> Bart.

Hi Bart,

Thanks for you suggestion. But the member hwq->id is an Unsigned 
integer. if you want to identify SDB mode and MCQ mode,  using "0" is 
enough, Or how about add string such as below?

ufshcd_command: MCQ: complete_rsp: 1d84000.ufshc: tag: 14, DB: 0x0, 
size: 32768, IS: 0, LBA: 5979448,opcode: 0x2a (WRITE_10),group_id: 0x0, 
hqid: 2

Ziqi
>