Linux kernel for uConsole
- C 97.1%
- Assembly 1.8%
- Shell 0.4%
- Makefile 0.3%
- Python 0.2%
2d9ee327ad
Currently memcmp() 64bytes version in powerpc will fall back to .Lshort
(compare per byte mode) if either src or dst address is not 8 bytes aligned.
It can be opmitized in 2 situations:
1) if both addresses are with the same offset with 8 bytes boundary:
memcmp() can compare the unaligned bytes within 8 bytes boundary firstly
and then compare the rest 8-bytes-aligned content with .Llong mode.
2) If src/dst addrs are not with the same offset of 8 bytes boundary:
memcmp() can align src addr with 8 bytes, increment dst addr accordingly,
then load src with aligned mode and load dst with unaligned mode.
This patch optmizes memcmp() behavior in the above 2 situations.
Tested with both little/big endian. Performance result below is based on
little endian.
Following is the test result with src/dst having the same offset case:
(a similar result was observed when src/dst having different offset):
(1) 256 bytes
Test with the existing tools/testing/selftests/powerpc/stringloops/memcmp:
- without patch
29.773018302 seconds time elapsed ( +- 0.09% )
- with patch
16.485568173 seconds time elapsed ( +- 0.02% )
-> There is ~+80% percent improvement
(2) 32 bytes
To observe performance impact on < 32 bytes, modify
tools/testing/selftests/powerpc/stringloops/memcmp.c with following:
-------
#include <string.h>
#include "utils.h"
-#define SIZE 256
+#define SIZE 32
#define ITERATIONS 10000
int test_memcmp(const void *s1, const void *s2, size_t n);
--------
- Without patch
0.244746482 seconds time elapsed ( +- 0.36%)
- with patch
0.215069477 seconds time elapsed ( +- 0.51%)
-> There is ～+13% improvement
(3) 0~8 bytes
To observe <8 bytes performance impact, modify
tools/testing/selftests/powerpc/stringloops/memcmp.c with following:
-------
#include <string.h>
#include "utils.h"
-#define SIZE 256
-#define ITERATIONS 10000
+#define SIZE 8
+#define ITERATIONS 1000000
int test_memcmp(const void *s1, const void *s2, size_t n);
-------
- Without patch
1.845642503 seconds time elapsed ( +- 0.12% )
- With patch
1.849767135 seconds time elapsed ( +- 0.26% )
-> They are nearly the same. (-0.2%)
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.