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/* Huge Page support. Linux implementation.
Copyright (C) 2021-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
#include <intprops.h>
#include <dirent.h>
#include <malloc-hugepages.h>
#include <not-cancel.h>
#include <sys/mman.h>
unsigned long int
__malloc_default_thp_pagesize (void)
{
int fd = __open64_nocancel (
"/sys/kernel/mm/transparent_hugepage/hpage_pmd_size", O_RDONLY);
if (fd == -1)
return 0;
char str[INT_BUFSIZE_BOUND (unsigned long int)];
ssize_t s = __read_nocancel (fd, str, sizeof (str));
__close_nocancel (fd);
if (s < 0)
return 0;
unsigned long int r = 0;
for (ssize_t i = 0; i < s; i++)
{
if (str[i] == '\n')
break;
r *= 10;
r += str[i] - '0';
}
return r;
}
enum malloc_thp_mode_t
__malloc_thp_mode (void)
{
int fd = __open64_nocancel ("/sys/kernel/mm/transparent_hugepage/enabled",
O_RDONLY);
if (fd == -1)
return malloc_thp_mode_not_supported;
static const char mode_always[] = "[always] madvise never\n";
static const char mode_madvise[] = "always [madvise] never\n";
static const char mode_never[] = "always madvise [never]\n";
char str[sizeof(mode_always)];
ssize_t s = __read_nocancel (fd, str, sizeof (str));
if (s >= sizeof str || s < 0)
return malloc_thp_mode_not_supported;
str[s] = '\0';
__close_nocancel (fd);
if (s == sizeof (mode_always) - 1)
{
if (strcmp (str, mode_always) == 0)
return malloc_thp_mode_always;
else if (strcmp (str, mode_madvise) == 0)
return malloc_thp_mode_madvise;
else if (strcmp (str, mode_never) == 0)
return malloc_thp_mode_never;
}
return malloc_thp_mode_not_supported;
}
static size_t
malloc_default_hugepage_size (void)
{
int fd = __open64_nocancel ("/proc/meminfo", O_RDONLY);
if (fd == -1)
return 0;
size_t hpsize = 0;
char buf[512];
off64_t off = 0;
while (1)
{
ssize_t r = __pread64_nocancel (fd, buf, sizeof (buf) - 1, off);
if (r < 0)
break;
buf[r] = '\0';
/* If the tag is not found, read the last line again. */
const char *s = strstr (buf, "Hugepagesize:");
if (s == NULL)
{
char *nl = strrchr (buf, '\n');
if (nl == NULL)
break;
off += (nl + 1) - buf;
continue;
}
/* The default huge page size is in the form:
Hugepagesize: NUMBER kB */
s += sizeof ("Hugepagesize: ") - 1;
for (int i = 0; (s[i] >= '0' && s[i] <= '9') || s[i] == ' '; i++)
{
if (s[i] == ' ')
continue;
hpsize *= 10;
hpsize += s[i] - '0';
}
hpsize *= 1024;
break;
}
__close_nocancel (fd);
return hpsize;
}
static inline int
hugepage_flags (size_t pagesize)
{
return MAP_HUGETLB | (__builtin_ctzll (pagesize) << MAP_HUGE_SHIFT);
}
void
__malloc_hugepage_config (size_t requested, size_t *pagesize, int *flags)
{
*pagesize = 0;
*flags = 0;
if (requested == 0)
{
*pagesize = malloc_default_hugepage_size ();
if (*pagesize != 0)
*flags = hugepage_flags (*pagesize);
return;
}
/* Each entry represents a supported huge page in the form of:
hugepages-<size>kB. */
int dirfd = __open64_nocancel ("/sys/kernel/mm/hugepages",
O_RDONLY | O_DIRECTORY, 0);
if (dirfd == -1)
return;
char buffer[1024];
while (true)
{
#if !IS_IN(libc)
# define __getdents64 getdents64
#endif
ssize_t ret = __getdents64 (dirfd, buffer, sizeof (buffer));
if (ret == -1)
break;
else if (ret == 0)
break;
bool found = false;
char *begin = buffer, *end = buffer + ret;
while (begin != end)
{
unsigned short int d_reclen;
memcpy (&d_reclen, begin + offsetof (struct dirent64, d_reclen),
sizeof (d_reclen));
const char *dname = begin + offsetof (struct dirent64, d_name);
begin += d_reclen;
if (dname[0] == '.'
|| strncmp (dname, "hugepages-", sizeof ("hugepages-") - 1) != 0)
continue;
size_t hpsize = 0;
const char *sizestr = dname + sizeof ("hugepages-") - 1;
for (int i = 0; sizestr[i] >= '0' && sizestr[i] <= '9'; i++)
{
hpsize *= 10;
hpsize += sizestr[i] - '0';
}
hpsize *= 1024;
if (hpsize == requested)
{
*pagesize = hpsize;
*flags = hugepage_flags (*pagesize);
found = true;
break;
}
}
if (found)
break;
}
__close_nocancel (dirfd);
}
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