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Nitesh Shetty 80c7378f94 io_uring/rsrc: send exact nr_segs for fixed buffer
Sending exact nr_segs, avoids bio split check and processing in
block layer, which takes around 5%[1] of overall CPU utilization.

In our setup, we see overall improvement of IOPS from 7.15M to 7.65M [2]
and 5% less CPU utilization.

[1]
     3.52%  io_uring         [kernel.kallsyms]     [k] bio_split_rw_at
     1.42%  io_uring         [kernel.kallsyms]     [k] bio_split_rw
     0.62%  io_uring         [kernel.kallsyms]     [k] bio_submit_split

[2]
sudo taskset -c 0,1 ./t/io_uring -b512 -d128 -c32 -s32 -p1 -F1 -B1 -n2
-r4 /dev/nvme0n1 /dev/nvme1n1

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
[Pavel: fixed for kbuf, rebased and reworked on top of cleanups]
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7a1a49a8d053bd617c244291d63dbfbc07afde36.1744882081.git.asml.silence@gmail.com
[axboe: fold in fix factoring in buf reg offset]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
History 2025-04-17 07:42:14 -06:00
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Linux kernel
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There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
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Please read the Documentation/process/changes.rst file, as it contains the
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