mm: huge_memory: a new debugfs interface for splitting THP tests (fa6c0231) · Commits · EulixOS / Software / Kernel

mm/huge_memory.c

+147 −8

Original line number	Diff line number	Diff line
		@@ -7,6 +7,7 @@

		#include <linux/mm.h>
		#include <linux/sched.h>
		#include <linux/sched/mm.h>
		#include <linux/sched/coredump.h>
		#include <linux/sched/numa_balancing.h>
		#include <linux/highmem.h>
		@@ -2915,16 +2916,14 @@ static struct shrinker deferred_split_shrinker = {
		};

		#ifdef CONFIG_DEBUG_FS
		static int split_huge_pages_set(void *data, u64 val)
		static void split_huge_pages_all(void)
		{
		struct zone *zone;
		struct page *page;
		unsigned long pfn, max_zone_pfn;
		unsigned long total = 0, split = 0;

		if (val != 1)
		return -EINVAL;

		pr_debug("Split all THPs\n");
		for_each_populated_zone(zone) {
		max_zone_pfn = zone_end_pfn(zone);
		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
		@@ -2948,15 +2947,155 @@ static int split_huge_pages_set(void *data, u64 val)
		unlock_page(page);
		next:
		put_page(page);
		cond_resched();
		}
		}

		pr_info("%lu of %lu THP split\n", split, total);
		pr_debug("%lu of %lu THP split\n", split, total);
		}

		return 0;
		static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
		{
		return vma_is_special_huge(vma) \|\| (vma->vm_flags & VM_IO) \|\|
		is_vm_hugetlb_page(vma);
		}

		static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
		unsigned long vaddr_end)
		{
		int ret = 0;
		struct task_struct *task;
		struct mm_struct *mm;
		unsigned long total = 0, split = 0;
		unsigned long addr;

		vaddr_start &= PAGE_MASK;
		vaddr_end &= PAGE_MASK;

		/* Find the task_struct from pid */
		rcu_read_lock();
		task = find_task_by_vpid(pid);
		if (!task) {
		rcu_read_unlock();
		ret = -ESRCH;
		goto out;
		}
		get_task_struct(task);
		rcu_read_unlock();

		/* Find the mm_struct */
		mm = get_task_mm(task);
		put_task_struct(task);

		if (!mm) {
		ret = -EINVAL;
		goto out;
		}

		pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
		pid, vaddr_start, vaddr_end);

		mmap_read_lock(mm);
		/*
		* always increase addr by PAGE_SIZE, since we could have a PTE page
		* table filled with PTE-mapped THPs, each of which is distinct.
		*/
		for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
		struct vm_area_struct *vma = find_vma(mm, addr);
		unsigned int follflags;
		struct page *page;

		if (!vma \|\| addr < vma->vm_start)
		break;

		/* skip special VMA and hugetlb VMA */
		if (vma_not_suitable_for_thp_split(vma)) {
		addr = vma->vm_end;
		continue;
		}

		/* FOLL_DUMP to ignore special (like zero) pages */
		follflags = FOLL_GET \| FOLL_DUMP;
		page = follow_page(vma, addr, follflags);

		if (IS_ERR(page))
		continue;
		if (!page)
		continue;

		if (!is_transparent_hugepage(page))
		goto next;

		total++;
		if (!can_split_huge_page(compound_head(page), NULL))
		goto next;

		if (!trylock_page(page))
		goto next;

		if (!split_huge_page(page))
		split++;

		unlock_page(page);
		next:
		put_page(page);
		cond_resched();
		}
		mmap_read_unlock(mm);
		mmput(mm);

		pr_debug("%lu of %lu THP split\n", split, total);

		out:
		return ret;
		}

		#define MAX_INPUT_BUF_SZ 255

		static ssize_t split_huge_pages_write(struct file file, const char __user buf,
		size_t count, loff_t *ppops)
		{
		static DEFINE_MUTEX(split_debug_mutex);
		ssize_t ret;
		char input_buf[MAX_INPUT_BUF_SZ]; /* hold pid, start_vaddr, end_vaddr */
		int pid;
		unsigned long vaddr_start, vaddr_end;

		ret = mutex_lock_interruptible(&split_debug_mutex);
		if (ret)
		return ret;

		ret = -EFAULT;

		memset(input_buf, 0, MAX_INPUT_BUF_SZ);
		if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
		goto out;

		input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
		ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
		if (ret == 1 && pid == 1) {
		split_huge_pages_all();
		ret = strlen(input_buf);
		goto out;
		} else if (ret != 3) {
		ret = -EINVAL;
		goto out;
		}
		DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
		"%llu\n");

		ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
		if (!ret)
		ret = strlen(input_buf);
		out:
		mutex_unlock(&split_debug_mutex);
		return ret;

		}

		static const struct file_operations split_huge_pages_fops = {
		.owner = THIS_MODULE,
		.write = split_huge_pages_write,
		.llseek = no_llseek,
		};

		static int __init split_huge_pages_debugfs(void)
		{

tools/testing/selftests/vm/.gitignore

+1 −0

Original line number	Diff line number	Diff line
		@@ -22,3 +22,4 @@ map_fixed_noreplace
		write_to_hugetlbfs
		hmm-tests
		local_config.*
		split_huge_page_test

tools/testing/selftests/vm/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -42,6 +42,7 @@ TEST_GEN_FILES += on-fault-limit
		TEST_GEN_FILES += thuge-gen
		TEST_GEN_FILES += transhuge-stress
		TEST_GEN_FILES += userfaultfd
		TEST_GEN_FILES += split_huge_page_test

		ifeq ($(MACHINE),x86_64)
		CAN_BUILD_I386 := $(shell ./../x86/check_cc.sh $(CC) ../x86/trivial_32bit_program.c -m32)

tools/testing/selftests/vm/split_huge_page_test.c

0 → 100644

+318 −0

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0
		/*
		* A test of splitting PMD THPs and PTE-mapped THPs from a specified virtual
		* address range in a process via <debugfs>/split_huge_pages interface.
		*/

		#define _GNU_SOURCE
		#include <stdio.h>
		#include <stdlib.h>
		#include <unistd.h>
		#include <inttypes.h>
		#include <string.h>
		#include <fcntl.h>
		#include <sys/mman.h>
		#include <malloc.h>
		#include <stdbool.h>

		uint64_t pagesize;
		unsigned int pageshift;
		uint64_t pmd_pagesize;

		#define PMD_SIZE_PATH "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size"
		#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
		#define SMAP_PATH "/proc/self/smaps"
		#define INPUT_MAX 80

		#define PFN_MASK ((1UL<<55)-1)
		#define KPF_THP (1UL<<22)

		int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
		{
		uint64_t paddr;
		uint64_t page_flags;

		if (pagemap_file) {
		pread(pagemap_file, &paddr, sizeof(paddr),
		((long)vaddr >> pageshift) * sizeof(paddr));

		if (kpageflags_file) {
		pread(kpageflags_file, &page_flags, sizeof(page_flags),
		(paddr & PFN_MASK) * sizeof(page_flags));

		return !!(page_flags & KPF_THP);
		}
		}
		return 0;
		}


		static uint64_t read_pmd_pagesize(void)
		{
		int fd;
		char buf[20];
		ssize_t num_read;

		fd = open(PMD_SIZE_PATH, O_RDONLY);
		if (fd == -1) {
		perror("Open hpage_pmd_size failed");
		exit(EXIT_FAILURE);
		}
		num_read = read(fd, buf, 19);
		if (num_read < 1) {
		close(fd);
		perror("Read hpage_pmd_size failed");
		exit(EXIT_FAILURE);
		}
		buf[num_read] = '\0';
		close(fd);

		return strtoul(buf, NULL, 10);
		}

		static int write_file(const char path, const char buf, size_t buflen)
		{
		int fd;
		ssize_t numwritten;

		fd = open(path, O_WRONLY);
		if (fd == -1)
		return 0;

		numwritten = write(fd, buf, buflen - 1);
		close(fd);
		if (numwritten < 1)
		return 0;

		return (unsigned int) numwritten;
		}

		static void write_debugfs(int pid, uint64_t vaddr_start, uint64_t vaddr_end)
		{
		char input[INPUT_MAX];
		int ret;

		ret = snprintf(input, INPUT_MAX, "%d,0x%lx,0x%lx", pid, vaddr_start,
		vaddr_end);
		if (ret >= INPUT_MAX) {
		printf("%s: Debugfs input is too long\n", __func__);
		exit(EXIT_FAILURE);
		}

		if (!write_file(SPLIT_DEBUGFS, input, ret + 1)) {
		perror(SPLIT_DEBUGFS);
		exit(EXIT_FAILURE);
		}
		}

		#define MAX_LINE_LENGTH 500

		static bool check_for_pattern(FILE fp, const char pattern, char *buf)
		{
		while (fgets(buf, MAX_LINE_LENGTH, fp) != NULL) {
		if (!strncmp(buf, pattern, strlen(pattern)))
		return true;
		}
		return false;
		}

		static uint64_t check_huge(void *addr)
		{
		uint64_t thp = 0;
		int ret;
		FILE *fp;
		char buffer[MAX_LINE_LENGTH];
		char addr_pattern[MAX_LINE_LENGTH];

		ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "%08lx-",
		(unsigned long) addr);
		if (ret >= MAX_LINE_LENGTH) {
		printf("%s: Pattern is too long\n", __func__);
		exit(EXIT_FAILURE);
		}


		fp = fopen(SMAP_PATH, "r");
		if (!fp) {
		printf("%s: Failed to open file %s\n", __func__, SMAP_PATH);
		exit(EXIT_FAILURE);
		}
		if (!check_for_pattern(fp, addr_pattern, buffer))
		goto err_out;

		/*
		* Fetch the AnonHugePages: in the same block and check the number of
		* hugepages.
		*/
		if (!check_for_pattern(fp, "AnonHugePages:", buffer))
		goto err_out;

		if (sscanf(buffer, "AnonHugePages:%10ld kB", &thp) != 1) {
		printf("Reading smap error\n");
		exit(EXIT_FAILURE);
		}

		err_out:
		fclose(fp);
		return thp;
		}

		void split_pmd_thp(void)
		{
		char *one_page;
		size_t len = 4 * pmd_pagesize;
		uint64_t thp_size;
		size_t i;

		one_page = memalign(pmd_pagesize, len);

		if (!one_page) {
		printf("Fail to allocate memory\n");
		exit(EXIT_FAILURE);
		}

		madvise(one_page, len, MADV_HUGEPAGE);

		for (i = 0; i < len; i++)
		one_page[i] = (char)i;

		thp_size = check_huge(one_page);
		if (!thp_size) {
		printf("No THP is allocated\n");
		exit(EXIT_FAILURE);
		}

		/* split all THPs */
		write_debugfs(getpid(), (uint64_t)one_page, (uint64_t)one_page + len);

		for (i = 0; i < len; i++)
		if (one_page[i] != (char)i) {
		printf("%ld byte corrupted\n", i);
		exit(EXIT_FAILURE);
		}


		thp_size = check_huge(one_page);
		if (thp_size) {
		printf("Still %ld kB AnonHugePages not split\n", thp_size);
		exit(EXIT_FAILURE);
		}

		printf("Split huge pages successful\n");
		free(one_page);
		}

		void split_pte_mapped_thp(void)
		{
		char one_page, pte_mapped, *pte_mapped2;
		size_t len = 4 * pmd_pagesize;
		uint64_t thp_size;
		size_t i;
		const char *pagemap_template = "/proc/%d/pagemap";
		const char *kpageflags_proc = "/proc/kpageflags";
		char pagemap_proc[255];
		int pagemap_fd;
		int kpageflags_fd;

		if (snprintf(pagemap_proc, 255, pagemap_template, getpid()) < 0) {
		perror("get pagemap proc error");
		exit(EXIT_FAILURE);
		}
		pagemap_fd = open(pagemap_proc, O_RDONLY);

		if (pagemap_fd == -1) {
		perror("read pagemap:");
		exit(EXIT_FAILURE);
		}

		kpageflags_fd = open(kpageflags_proc, O_RDONLY);

		if (kpageflags_fd == -1) {
		perror("read kpageflags:");
		exit(EXIT_FAILURE);
		}

		one_page = mmap((void *)(1UL << 30), len, PROT_READ \| PROT_WRITE,
		MAP_ANONYMOUS \| MAP_PRIVATE, -1, 0);

		madvise(one_page, len, MADV_HUGEPAGE);

		for (i = 0; i < len; i++)
		one_page[i] = (char)i;

		thp_size = check_huge(one_page);
		if (!thp_size) {
		printf("No THP is allocated\n");
		exit(EXIT_FAILURE);
		}

		/* remap the first pagesize of first THP */
		pte_mapped = mremap(one_page, pagesize, pagesize, MREMAP_MAYMOVE);

		/* remap the Nth pagesize of Nth THP */
		for (i = 1; i < 4; i++) {
		pte_mapped2 = mremap(one_page + pmd_pagesize * i + pagesize * i,
		pagesize, pagesize,
		MREMAP_MAYMOVE\|MREMAP_FIXED,
		pte_mapped + pagesize * i);
		if (pte_mapped2 == (char *)-1) {
		perror("mremap failed");
		exit(EXIT_FAILURE);
		}
		}

		/* smap does not show THPs after mremap, use kpageflags instead */
		thp_size = 0;
		for (i = 0; i < pagesize * 4; i++)
		if (i % pagesize == 0 &&
		is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
		thp_size++;

		if (thp_size != 4) {
		printf("Some THPs are missing during mremap\n");
		exit(EXIT_FAILURE);
		}

		/* split all remapped THPs */
		write_debugfs(getpid(), (uint64_t)pte_mapped,
		(uint64_t)pte_mapped + pagesize * 4);

		/* smap does not show THPs after mremap, use kpageflags instead */
		thp_size = 0;
		for (i = 0; i < pagesize * 4; i++) {
		if (pte_mapped[i] != (char)i) {
		printf("%ld byte corrupted\n", i);
		exit(EXIT_FAILURE);
		}
		if (i % pagesize == 0 &&
		is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
		thp_size++;
		}

		if (thp_size) {
		printf("Still %ld THPs not split\n", thp_size);
		exit(EXIT_FAILURE);
		}

		printf("Split PTE-mapped huge pages successful\n");
		munmap(one_page, len);
		close(pagemap_fd);
		close(kpageflags_fd);
		}

		int main(int argc, char **argv)
		{
		if (geteuid() != 0) {
		printf("Please run the benchmark as root\n");
		exit(EXIT_FAILURE);
		}

		pagesize = getpagesize();
		pageshift = ffs(pagesize) - 1;
		pmd_pagesize = read_pmd_pagesize();

		split_pmd_thp();
		split_pte_mapped_thp();

		return 0;
		}