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bda9c7d92f
seq_printf is costly. For each block device, 19 decimal values are yielded in /proc/diskstats via seq_printf. On a system with 16 logical block devices, profiling for open/read/close sequences shows seq_printf took ~75% samples of diskstats_show: diskstats_show(92.626% 2269372/2450040) seq_printf(76.026% 1725313/2269372) vsnprintf(99.163% 1710866/1725313) format_decode(26.597% 455040/1710866) number(19.554% 334542/1710866) memcpy_orig(4.183% 71570/1710866) ... srso_return_thunk(0.009% 148/1725313) part_stat_read_all(8.030% 182236/2269372) One million rounds of open/read/close /proc/diskstats takes: real 0m37.687s user 0m0.264s sys 0m32.911s On average, each sequence tooks ~0.032ms With this patch, most decimal values are yield via seq_put_decimal_ull, performance is significantly improved: real 0m20.792s user 0m0.316s sys 0m20.463s On average, each sequence tooks ~0.020ms, a ~37.5% improvement. Signed-off-by: David Wang <00107082@163.com> Link: https://lore.kernel.org/r/20241108054500.4251-1-00107082@163.com Signed-off-by: Jens Axboe <axboe@kernel.dk> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText 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.