Difference between
modified post e1ff71 by Anonymous on Tue 6th Sep 2022 15:27
original post adc by Anonymous on Tue 6th Sep 2022 15:19
Download diff
Show old version | new version | both versions

/*

1	1	/*
2	2	* hugepage_alloc_test1.c - test the availabilty of
3	3	* largepages/hugepages
4	4	*
5	5	* Written by Roland Mainz <roland.mainz@nrubsig.org>
6	6	*/
7	7
8	8	#include <stdlib.h>
9	9	#include <stdio.h>
10	10	#include <stdbool.h>
11	11	#include <errno.h>
12	12	#include <fcntl.h>
13	13	#include <unistd.h>
14	14
15	15	#include <sys/mman.h>
16	16	#include <sys/stat.h>
17	17
18	18	#include <linux/mman.h>
19	19
20	20	/*
21	21	* Before using this Linux 5.10.0-13-rt-686-pae requires that "root"
22	22	* reserves hugepages like this:
23	23	*
24	24	* $ printf '128' > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
25	25	* $ cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
26	26	* 128
27	27	*
28	28	* Notes:
29	29	* - Terminology: UNIX uses the term "largepages", Linux defiantly
30	30	* uses "hugepages"
31	31	* - the value is the number of MMU (large-/huge-)pages, NOT the
32	32	* number of bytes.
33	33	* - $ /usr/bin/pagesize -a # can inform you which pagesizes are
34	34	* available (i686 usually has { 4k, 2M } pagesizes, SPARCv9 has
35	35	* { 8k, 64k, 4M, 32M, ... } )
36	36	*/
37	37
38	38	/* Linux-specific version */
39	39	ssize_t get_number_of_free_hugepages(void)
40	40	{
41	41	int dirfd;
42	42	int fd;
43	43	/*
44	44	* \|round(log10(18446744073709551615))\| is \|19\| on a 64bit
45	45	* system, so \|128\| should be enough (including sign)
46	46	*/
47	47	char buf[128];
48	48	ssize_t numpages;
49	49	ssize_t rs; /* read size */
50	50
51	51	/*
52	52	* extra step here, since real-world applications likely
53	53	* want to look at "nr_hugepages" etc, too
54	54	*/
55	55	dirfd = open("/sys/kernel/mm/hugepages/hugepages-2048kB/",
56	56	O_DIRECTORY);
57	57	if (dirfd < 0) {
58	58	perror("open sysfs hugepage dir");
59	59	return -1;
60	60	}
61	61
62	62	fd = openat(dirfd, "free_hugepages", O_RDONLY);
63	63	if (fd < 0) {
64	64	perror("open sysfs hugepage free pages file");
65	65	(void)close(dirfd);
66	66	return -1;
67	67	}
68	68	rs = read(fd, buf, sizeof(buf));
69	69	if (rs < 0) {
70	70	perror("read error sysfs hugepage free pages file");
71	71	(void)close(dirfd);
72	72	(void)close(fd);
73	73	return -1;
74	74	}
75	75
76	76	(void)close(dirfd);
77	77	(void)close(fd);
78	78
79	79	buf[rs] = '\0';
80	80	#if MYDEBUG
81	81	if ((rs > 0) && (buf[rs-1] == '\n'))
82	82	buf[rs-1] = '\0';
83	83	(void)printf("string returned: \|%s\|\n", buf);
84	84	#endif /* MYDEBUG */
85	85
86	86	errno = 0;
87	87	numpages = strtol(buf, NULL, 10);
88	88	if (errno != 0) {
89	89	perror("error parsing value of free hugepages");
90	90	return -1;
91	91	}
92	92
93	93	return numpages;
94	94	}
95	95
96	96
97	97	int main(int ac, char *av[])
98	98	{
99	99	void *p;
100	100	int saved_errno;
101	101	#define TEST_NUM_ALLOC_PAGES (32)
102	102	const size_t size = TEST_NUM_ALLOC_PAGES10241024;
103	103	ssize_t free_numpages;
104	104
105	105	(void)puts("#start.");
106	106
107	107	free_numpages = get_number_of_free_hugepages();
108	108
109	109	if (free_numpages < (TEST_NUM_ALLOC_PAGES+8)) {
110	110	(void)fprintf(stderr,
111	111	"not enough hugepages, currently free %ld\n",
112	112	(long)free_numpages);
113	113	return EXIT_FAILURE;
114	114	}
115	115
116	116	/* get mmap()'ed memory with hugepage attribute */
117	117	p = mmap(0,
118	118	size,
119	119	PROT_READ\|PROT_WRITE,
120	120	MAP_PRIVATE\|MAP_ANONYMOUS\|MAP_HUGETLB, -1, 0);
121	121	saved_errno = errno;
122	122	if (p == MAP_FAILED) {
123	123	perror("mmap");
124	124	return EXIT_FAILURE;
125	125	}
126	126
127	127	(void)printf("map address = 0x%lx, errno=%d\n",
128	128	(unsigned long)p, (int)saved_errno);
129	129
130	130	/* use memory */
131	131	volatile unsigned char *c = p;
132	132	for (size_t i = 0 ; i < size ; i++) {
133	133	c[i] = (unsigned char)(i % 255);
134	134	}
135	135
136	136	#if MYDEBUG_USE_PROC_SMAPS
137	137	/*
138	138	* Wait here so we can check out
139	139	* $ cat /proc/$mypid/smaps \| fgrep -i huge #
140	140	*/
141	141	sleep(1000);
142	142	#endif /* MYDEBUG_USE_PROC_SMAPS */
143	143
144	144	if (munmap(p, size) == -1)
145	145	perror("munmap");
146	146
147	147	(void)puts("#done.");
148	148
149	149	return EXIT_SUCCESS;
150	150	}
151	151