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8cfa67b4d9
seq_printf() is slow and it can be replaced by memset() in this case.
== test.py
num = 0
with open("/proc/1/maps") as f:
while num < 10000 :
data = f.read()
f.seek(0, 0)
num = num + 1
==
== Before patch ==
$ time python test.py
real 0m0.986s
user 0m0.279s
sys 0m0.707s
== After patch ==
$ time python test.py
real 0m0.932s
user 0m0.261s
sys 0m0.669s
$ perf record -g python test.py
== Before patch ==
- 47.35% 3.38% python [kernel.kallsyms] [k] show_map_vma.isra.23
- 43.97% show_map_vma.isra.23
+ 20.84% seq_path
- 15.73% show_vma_header_prefix
+ 6.96% seq_pad
+ 2.94% __GI___libc_read
== After patch ==
- 44.01% 0.34% python [kernel.kallsyms] [k] show_pid_map
- 43.67% show_pid_map
- 42.91% show_map_vma.isra.23
+ 21.55% seq_path
- 15.68% show_vma_header_prefix
+ 2.08% seq_pad
0.55% seq_putc
Link: http://lkml.kernel.org/r/20180112185812.7710-2-avagin@openvz.org
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.