Skip to content

setup: dynamically detect default huge page size #1600

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Kprateek283 wants to merge 1 commit into
base: master
Choose a base branch
from
+68 −16
Open

setup: dynamically detect default huge page size #1600

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
84 changes: 68 additions & 16 deletions src/setup.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -220,15 +220,67 @@ __cold int io_uring_ring_dontfork(struct io_uring *ring)
return 0;
}

#ifndef MAP_HUGE_SHIFT
#define MAP_HUGE_SHIFT 26
#endif
#ifndef MAP_HUGE_2MB
#define MAP_HUGE_2MB (21U << MAP_HUGE_SHIFT)
#endif

/* FIXME */
static size_t huge_page_size = 2 * 1024 * 1024;
static size_t get_huge_page_size(void)
{
static size_t hps;
size_t ret = 2 * 1024 * 1024; /* fallback: 2MB */
char buf[4096];
char *p, *end;
unsigned long val;
ssize_t n;
int fd;

if (hps)
return hps;

fd = __sys_open("/proc/meminfo", O_RDONLY, 0);
if (fd < 0)
goto out;

n = __sys_read(fd, buf, sizeof(buf) - 1);
__sys_close(fd);
if (n <= 0)
goto out;
buf[n] = '\0';

/*
* Scan line-by-line for "Hugepagesize:". We avoid strstr() and
* memcmp() because they are not available in CONFIG_NOLIBC builds.
*/
p = buf;
end = buf + n;
while (p < end) {
/* Check if this line starts with "Hugepagesize:" (13 chars) */
if (p + 13 <= end &&
p[0] == 'H' && p[1] == 'u' && p[2] == 'g' &&
p[3] == 'e' && p[4] == 'p' && p[5] == 'a' &&
p[6] == 'g' && p[7] == 'e' && p[8] == 's' &&
p[9] == 'i' && p[10] == 'z' && p[11] == 'e' &&
p[12] == ':') {
p += 13;
while (p < end && (*p == ' ' || *p == '\t'))
p++;
val = 0;
while (p < end && *p >= '0' && *p <= '9') {
val = val * 10 + (*p - '0');
p++;
}
if (val)
ret = val * 1024; /* kB -> bytes */
break;
}
/* Advance to next line */
while (p < end && *p != '\n')
p++;
if (p < end)
p++;
}
out:
hps = ret;
return hps;
}


#define KRING_SIZE 64

Expand Down Expand Up @@ -261,13 +313,13 @@ static int io_uring_alloc_huge(unsigned entries, struct io_uring_params *p,
mem_used = (mem_used + page_size - 1) & ~(page_size - 1);

/*
* A maxed-out number of CQ entries with IORING_SETUP_CQE32 fills a 2MB
* huge page by itself, so the SQ entries won't fit in the same huge
* page. For SQEs, that shouldn't be possible given KERN_MAX_ENTRIES,
* A maxed-out number of CQ entries with IORING_SETUP_CQE32 can fill a
* single huge page by itself, so the SQ entries won't fit in the same
* huge page. For SQEs, that shouldn't be possible given KERN_MAX_ENTRIES,
* but check that too to future-proof (e.g. against different huge page
* sizes). Bail out early so we don't overrun.
*/
if (!buf && (sqes_mem > huge_page_size || ring_mem > huge_page_size))
if (!buf && (sqes_mem > get_huge_page_size() || ring_mem > get_huge_page_size()))
return -ENOMEM;

if (buf) {
Expand All @@ -279,8 +331,8 @@ static int io_uring_alloc_huge(unsigned entries, struct io_uring_params *p,
if (sqes_mem <= page_size)
buf_size = page_size;
else {
buf_size = huge_page_size;
map_hugetlb = MAP_HUGETLB | MAP_HUGE_2MB;
buf_size = get_huge_page_size();
map_hugetlb = MAP_HUGETLB;
}
sqes_size = buf_size;
ptr = __sys_mmap(NULL, sqes_size, PROT_READ|PROT_WRITE,
Expand All @@ -302,8 +354,8 @@ static int io_uring_alloc_huge(unsigned entries, struct io_uring_params *p,
if (ring_mem <= page_size)
buf_size = page_size;
else {
buf_size = huge_page_size;
map_hugetlb = MAP_HUGETLB | MAP_HUGE_2MB;
buf_size = get_huge_page_size();
map_hugetlb = MAP_HUGETLB;
}
ptr = __sys_mmap(NULL, buf_size, PROT_READ|PROT_WRITE,
MAP_SHARED|MAP_ANONYMOUS|map_hugetlb,
Expand Down
Loading