Linux kernel modifications for the Kernel Hacking exam
a2a84e3633
This patch simplifies TLB load, store and modify exception handlers:
1. Reduce instructions, such as alu/csr and memory access;
2. Execute tlb search instruction only in the fast path;
3. Return directly from the fast path for both normal and huge pages;
4. Re-tab the assembly for better vertical alignment.
And fixes the concurrent modification issue of fast path for huge pages.
This issue will occur in the following steps:
CPU-1 (In TLB exception) CPU-2 (In THP splitting)
1: Load PMD entry (HUGE=1)
2: Goto huge path
3: Store PMD entry (HUGE=0)
4: Reload PMD entry (HUGE=0)
5: Fill TLB entry (PA is incorrect)
This patch also slightly improves the TLB processing performance:
* Normal pages: 2.15%, Huge pages: 1.70%.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
int main(int argc, char *argv[])
{
size_t page_size;
size_t mem_size;
size_t off;
void *base;
int flags;
int i;
if (argc < 2) {
fprintf(stderr, "%s MEM_SIZE [HUGE]\n", argv[0]);
return -1;
}
page_size = sysconf(_SC_PAGESIZE);
flags = MAP_PRIVATE | MAP_ANONYMOUS;
mem_size = strtoul(argv[1], NULL, 10);
if (argc > 2)
flags |= MAP_HUGETLB;
for (i = 0; i < 10; i++) {
base = mmap(NULL, mem_size, PROT_READ, flags, -1, 0);
if (base == MAP_FAILED) {
fprintf(stderr, "Map memory failed!\n");
return -1;
}
for (off = 0; off < mem_size; off += page_size)
*(volatile int *)(base + off);
munmap(base, mem_size);
}
return 0;
}
Signed-off-by: Rui Wang <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| 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.
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.