Re: [RFC] traceevent/block: Add REQ_ATOMIC flag to block trace events

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

Ritesh Harjani (IBM) <ritesh.list@gmail.com> writes:

> John Garry <john.g.garry@oracle.com> writes:
>
>> On 03/04/2025 06:28, Ritesh Harjani (IBM) wrote:
>>> Filesystems like XFS can implement atomic write I/O using either REQ_ATOMIC
>>> flag set in the bio or via CoW operation. It will be useful if we have a
>>> flag in trace events to distinguish between the two. 
>>
>> I suppose that this could be useful. So far I test with block driver 
>> traces, i.e. NVMe or SCSI internal traces, just to ensure that we see 
>> the requests sent as expected
>>
>
> Right.
>
>> This patch adds
>>> char 'a' to rwbs field of the trace events if REQ_ATOMIC flag is set in
>>> the bio.
>>
>> All others use uppercase characters, so I suggest that you continue to 
>> use that.
>
> It will be good to know on whether only uppercase characters are allowed
> or we are good with smallcase characters too? 
>
>> Since 'A' is already used, how about 'U' for untorn? Or 'T' 
>> for aTOMic :)
>>
>
> If 'a' is not allowed, then we can change it to 'T' maybe.
>

Gentle ping on this.. Any comments/feedback?

It will be good to have these trace events with an identifier to
differentiate between reqs/bios submitted with REQ_ATOMIC flag.

-ritesh

> -ritesh
>
>
>>> 
>>> <W/ REQ_ATOMIC>
>>> =================
>>> xfs_io-1107    [002] .....   406.206441: block_rq_issue: 8,48 WSa 16384 () 768 + 32 none,0,0 [xfs_io]
>>> <idle>-0       [002] ..s1.   406.209918: block_rq_complete: 8,48 WSa () 768 + 32 none,0,0 [0]
>>> 
>>> <W/O REQ_ATOMIC>
>>> ===============
>>> xfs_io-1108    [002] .....   411.212317: block_rq_issue: 8,48 WS 16384 () 1024 + 32 none,0,0 [xfs_io]
>>> <idle>-0       [002] ..s1.   411.215842: block_rq_complete: 8,48 WS () 1024 + 32 none,0,0 [0]
>>>