diff options
author | Alexey Dobriyan | 2020-04-06 20:09:01 -0700 |
---|---|---|
committer | Linus Torvalds | 2020-04-07 10:43:42 -0700 |
commit | d919b33dafb3e222d23671b2bb06d119aede625f (patch) | |
tree | 4615344609db28df7643d80776e5a1a8c7457442 /include | |
parent | 904f394e2e9fd362dc78d58646b85c4cf6c87cac (diff) |
proc: faster open/read/close with "permanent" files
Now that "struct proc_ops" exist we can start putting there stuff which
could not fly with VFS "struct file_operations"...
Most of fs/proc/inode.c file is dedicated to make open/read/.../close
reliable in the event of disappearing /proc entries which usually happens
if module is getting removed. Files like /proc/cpuinfo which never
disappear simply do not need such protection.
Save 2 atomic ops, 1 allocation, 1 free per open/read/close sequence for such
"permanent" files.
Enable "permanent" flag for
/proc/cpuinfo
/proc/kmsg
/proc/modules
/proc/slabinfo
/proc/stat
/proc/sysvipc/*
/proc/swaps
More will come once I figure out foolproof way to prevent out module
authors from marking their stuff "permanent" for performance reasons
when it is not.
This should help with scalability: benchmark is "read /proc/cpuinfo R times
by N threads scattered over the system".
N R t, s (before) t, s (after)
-----------------------------------------------------
64 4096 1.582458 1.530502 -3.2%
256 4096 6.371926 6.125168 -3.9%
1024 4096 25.64888 24.47528 -4.6%
Benchmark source:
#include <chrono>
#include <iostream>
#include <thread>
#include <vector>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
const int NR_CPUS = sysconf(_SC_NPROCESSORS_ONLN);
int N;
const char *filename;
int R;
int xxx = 0;
int glue(int n)
{
cpu_set_t m;
CPU_ZERO(&m);
CPU_SET(n, &m);
return sched_setaffinity(0, sizeof(cpu_set_t), &m);
}
void f(int n)
{
glue(n % NR_CPUS);
while (*(volatile int *)&xxx == 0) {
}
for (int i = 0; i < R; i++) {
int fd = open(filename, O_RDONLY);
char buf[4096];
ssize_t rv = read(fd, buf, sizeof(buf));
asm volatile ("" :: "g" (rv));
close(fd);
}
}
int main(int argc, char *argv[])
{
if (argc < 4) {
std::cerr << "usage: " << argv[0] << ' ' << "N /proc/filename R
";
return 1;
}
N = atoi(argv[1]);
filename = argv[2];
R = atoi(argv[3]);
for (int i = 0; i < NR_CPUS; i++) {
if (glue(i) == 0)
break;
}
std::vector<std::thread> T;
T.reserve(N);
for (int i = 0; i < N; i++) {
T.emplace_back(f, i);
}
auto t0 = std::chrono::system_clock::now();
{
*(volatile int *)&xxx = 1;
for (auto& t: T) {
t.join();
}
}
auto t1 = std::chrono::system_clock::now();
std::chrono::duration<double> dt = t1 - t0;
std::cout << dt.count() << '
';
return 0;
}
P.S.:
Explicit randomization marker is added because adding non-function pointer
will silently disable structure layout randomization.
[akpm@linux-foundation.org: coding style fixes]
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Joe Perches <joe@perches.com>
Link: http://lkml.kernel.org/r/20200222201539.GA22576@avx2
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/proc_fs.h | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index 40a7982b7285..45c05fd9c99d 100644 --- a/include/linux/proc_fs.h +++ b/include/linux/proc_fs.h @@ -5,6 +5,7 @@ #ifndef _LINUX_PROC_FS_H #define _LINUX_PROC_FS_H +#include <linux/compiler.h> #include <linux/types.h> #include <linux/fs.h> @@ -12,7 +13,21 @@ struct proc_dir_entry; struct seq_file; struct seq_operations; +enum { + /* + * All /proc entries using this ->proc_ops instance are never removed. + * + * If in doubt, ignore this flag. + */ +#ifdef MODULE + PROC_ENTRY_PERMANENT = 0U, +#else + PROC_ENTRY_PERMANENT = 1U << 0, +#endif +}; + struct proc_ops { + unsigned int proc_flags; int (*proc_open)(struct inode *, struct file *); ssize_t (*proc_read)(struct file *, char __user *, size_t, loff_t *); ssize_t (*proc_write)(struct file *, const char __user *, size_t, loff_t *); @@ -25,7 +40,7 @@ struct proc_ops { #endif int (*proc_mmap)(struct file *, struct vm_area_struct *); unsigned long (*proc_get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); -}; +} __randomize_layout; #ifdef CONFIG_PROC_FS |