Re: [RFC PATCH] iomap: add fast read path for small direct I/O

["Fengnan" <changfengnan@bytedance.com>]

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在 2026/4/22 06:36, Dave Chinner 写道:
> On Tue, Apr 21, 2026 at 11:19:31AM +0800, Fengnan wrote:
>> 在 2026/4/21 07:59, Dave Chinner 写道:
>>> I'm clearly missing something here. I'm trying to work out why the
>>> profiles show what they do, but there's differences between them
>>> that do make obvious sense to me.
>>>
>>> It would also be useful to have XFS profiles, because it has a
>>> larger CPU cache footprint than ext4. If what the profiles are
>>> showing is a result of CPU cache residency artifacts, then we'll see
>>> different profile (and, potentially, performance) artifacts with
>>> XFS...
>> The XFS flame graph is also attached now.
>> IOPS: 1.92M->2.3M.
> The callchains in both XFS flame graphs are completely bogus:
>
> <io_uring entry>
> ....
> io_read
> __io_read
> xfs_inode_free_eofblocks
> xfs_prep_free_cowblocks
> iomap_dio_rw
> iomap_dio_simple_read
> xfs_mountfs
> ....
>
> Can you regenerate the profiles, please, and this time check that
> they make sense before posting them?

Sorry, I didn't check xfs before, new flame graph is attached
now, now the callchains make sense.

>
> -Dave.

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