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abc54d6343
io_uring manipulates references twice for each request, and hence is very
sensitive to performance of the reference count. This commit borrows a
trick from:
commit f958d7b528
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu Apr 11 10:06:20 2019 -0700
mm: make page ref count overflow check tighter and more explicit
and switches to atomic_t for references, while still retaining overflow
and underflow checks.
This is good for a 2-3% increase in peak IOPS on a single core. Before:
IOPS=2970879, IOS/call=31/31, inflight=128 (128)
IOPS=2952597, IOS/call=31/31, inflight=128 (128)
IOPS=2943904, IOS/call=31/31, inflight=128 (128)
IOPS=2930006, IOS/call=31/31, inflight=96 (96)
and after:
IOPS=3054354, IOS/call=31/31, inflight=128 (128)
IOPS=3059038, IOS/call=31/31, inflight=128 (128)
IOPS=3060320, IOS/call=31/31, inflight=128 (128)
IOPS=3068256, IOS/call=31/31, inflight=96 (96)
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
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In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.