On 12/30/2025 6:27 PM, Chao Yu wrote:
Hi Jeuk,
On 12/29/2025 2:33 PM, Jeuk Kim wrote:
Hi F2FS maintainers,
Sorry for the duplicate — I’m resending this because the previous
message was sent in HTML format.
I’ve been looking into the DIO allocation path in f2fs, specifically
when a DIO write needs to allocate new blocks (e.g., hole-filling).
From f2fs_map_blocks() through __allocate_data_block() →
f2fs_allocate_data_block(), it seems each block allocation is handled
one-by-one, taking curseg_lock/curseg_mutex and the SIT sentry lock
per block.
I’m wondering whether batching allocations (a bounded batch, e.g., a
small run within the current segment) could be feasible in the DIO
path. My intuition is that with multiple threads doing DIO, reducing
per-block lock contention and improving sequentiality could help
throughput.
I agree w/ you.
Questions:
Is there a technical or correctness reason that makes batching for DIO
infeasible (e.g., LFS/SSR/GC interactions, summary/SIT update
ordering, etc.)?
Or is this simply an optimization that hasn’t been implemented?
I've implemented a prototype of multiple block allocation for any
potential
use cases: pinfile fallocation, direct IO and buffered IO. I can see
benefits
from my previous test.
I plan to upstream all implementations, but I think I need more time
to clean
up the draft codes and check all corner cases.
You can check the MBA implementation for pinfile use case in below
link, I
guess this version is close to upstream.
https://github.com/chaseyu/f2fs-dev/commits/feature/inbatch_write
Thanks,
If this seems acceptable, would you consider patches in this direction?
If there are prior discussions or known issues on this, I’d
appreciate pointers.
Thanks for your time.
Best regards,
Jeuk Kim
Hi Chao,
Thanks a lot for sharing this and the link.
Good to hear you’ve seen benefits from the MBA prototype.
I’ll look into the pinfile implementation and try testing it on my side.
Thanks,
Jeuk
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