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Message-ID: <877cm9xap1.fsf@nvdebian.thelocal>
Date: Thu, 23 Nov 2023 17:07:28 +1100
From: Alistair Popple <apopple@...dia.com>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Matthew Wilcox <willy@...radead.org>,
Yin Fengwei <fengwei.yin@...el.com>,
David Hildenbrand <david@...hat.com>,
Yu Zhao <yuzhao@...gle.com>,
Catalin Marinas <catalin.marinas@....com>,
Anshuman Khandual <anshuman.khandual@....com>,
Yang Shi <shy828301@...il.com>,
"Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
Luis Chamberlain <mcgrof@...nel.org>,
Itaru Kitayama <itaru.kitayama@...il.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
John Hubbard <jhubbard@...dia.com>,
David Rientjes <rientjes@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Hugh Dickins <hughd@...gle.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>, linux-mm@...ck.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v7 06/10] selftests/mm: Factor out thp settings
management
Ryan Roberts <ryan.roberts@....com> writes:
> The khugepaged test has a useful framework for save/restore/pop/push of
> all thp settings via the sysfs interface. This will be useful to
> explicitly control small-sized THP settings in other tests, so let's
> move it out of khugepaged and into its own thp_settings.[c|h] utility.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
I've only glanced at the code as I assume it is a straight forward
cut-and-paste with no behavioural change. At least I didn't observe any
change running the khugepage test on my x86_64 development machine so
feel free to add:
Tested-by: Alistair Popple <apopple@...dia.com>
> ---
> tools/testing/selftests/mm/Makefile | 4 +-
> tools/testing/selftests/mm/khugepaged.c | 346 ++--------------------
> tools/testing/selftests/mm/thp_settings.c | 296 ++++++++++++++++++
> tools/testing/selftests/mm/thp_settings.h | 71 +++++
> 4 files changed, 391 insertions(+), 326 deletions(-)
> create mode 100644 tools/testing/selftests/mm/thp_settings.c
> create mode 100644 tools/testing/selftests/mm/thp_settings.h
>
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index 78dfec8bc676..a3eb20c186e7 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -117,8 +117,8 @@ TEST_FILES += va_high_addr_switch.sh
>
> include ../lib.mk
>
> -$(TEST_GEN_PROGS): vm_util.c
> -$(TEST_GEN_FILES): vm_util.c
> +$(TEST_GEN_PROGS): vm_util.c thp_settings.c
> +$(TEST_GEN_FILES): vm_util.c thp_settings.c
>
> $(OUTPUT)/uffd-stress: uffd-common.c
> $(OUTPUT)/uffd-unit-tests: uffd-common.c
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index fc47a1c4944c..b15e7fd70176 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -22,13 +22,13 @@
> #include "linux/magic.h"
>
> #include "vm_util.h"
> +#include "thp_settings.h"
>
> #define BASE_ADDR ((void *)(1UL << 30))
> static unsigned long hpage_pmd_size;
> static unsigned long page_size;
> static int hpage_pmd_nr;
>
> -#define THP_SYSFS "/sys/kernel/mm/transparent_hugepage/"
> #define PID_SMAPS "/proc/self/smaps"
> #define TEST_FILE "collapse_test_file"
>
> @@ -71,78 +71,7 @@ struct file_info {
> };
>
> static struct file_info finfo;
> -
> -enum thp_enabled {
> - THP_ALWAYS,
> - THP_MADVISE,
> - THP_NEVER,
> -};
> -
> -static const char *thp_enabled_strings[] = {
> - "always",
> - "madvise",
> - "never",
> - NULL
> -};
> -
> -enum thp_defrag {
> - THP_DEFRAG_ALWAYS,
> - THP_DEFRAG_DEFER,
> - THP_DEFRAG_DEFER_MADVISE,
> - THP_DEFRAG_MADVISE,
> - THP_DEFRAG_NEVER,
> -};
> -
> -static const char *thp_defrag_strings[] = {
> - "always",
> - "defer",
> - "defer+madvise",
> - "madvise",
> - "never",
> - NULL
> -};
> -
> -enum shmem_enabled {
> - SHMEM_ALWAYS,
> - SHMEM_WITHIN_SIZE,
> - SHMEM_ADVISE,
> - SHMEM_NEVER,
> - SHMEM_DENY,
> - SHMEM_FORCE,
> -};
> -
> -static const char *shmem_enabled_strings[] = {
> - "always",
> - "within_size",
> - "advise",
> - "never",
> - "deny",
> - "force",
> - NULL
> -};
> -
> -struct khugepaged_settings {
> - bool defrag;
> - unsigned int alloc_sleep_millisecs;
> - unsigned int scan_sleep_millisecs;
> - unsigned int max_ptes_none;
> - unsigned int max_ptes_swap;
> - unsigned int max_ptes_shared;
> - unsigned long pages_to_scan;
> -};
> -
> -struct settings {
> - enum thp_enabled thp_enabled;
> - enum thp_defrag thp_defrag;
> - enum shmem_enabled shmem_enabled;
> - bool use_zero_page;
> - struct khugepaged_settings khugepaged;
> - unsigned long read_ahead_kb;
> -};
> -
> -static struct settings saved_settings;
> static bool skip_settings_restore;
> -
> static int exit_status;
>
> static void success(const char *msg)
> @@ -161,226 +90,13 @@ static void skip(const char *msg)
> printf(" \e[33m%s\e[0m\n", msg);
> }
>
> -static int read_file(const char *path, char *buf, size_t buflen)
> -{
> - int fd;
> - ssize_t numread;
> -
> - fd = open(path, O_RDONLY);
> - if (fd == -1)
> - return 0;
> -
> - numread = read(fd, buf, buflen - 1);
> - if (numread < 1) {
> - close(fd);
> - return 0;
> - }
> -
> - buf[numread] = '\0';
> - close(fd);
> -
> - return (unsigned int) numread;
> -}
> -
> -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) {
> - printf("open(%s)\n", path);
> - exit(EXIT_FAILURE);
> - return 0;
> - }
> -
> - numwritten = write(fd, buf, buflen - 1);
> - close(fd);
> - if (numwritten < 1) {
> - printf("write(%s)\n", buf);
> - exit(EXIT_FAILURE);
> - return 0;
> - }
> -
> - return (unsigned int) numwritten;
> -}
> -
> -static int read_string(const char *name, const char *strings[])
> -{
> - char path[PATH_MAX];
> - char buf[256];
> - char *c;
> - int ret;
> -
> - ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> - if (ret >= PATH_MAX) {
> - printf("%s: Pathname is too long\n", __func__);
> - exit(EXIT_FAILURE);
> - }
> -
> - if (!read_file(path, buf, sizeof(buf))) {
> - perror(path);
> - exit(EXIT_FAILURE);
> - }
> -
> - c = strchr(buf, '[');
> - if (!c) {
> - printf("%s: Parse failure\n", __func__);
> - exit(EXIT_FAILURE);
> - }
> -
> - c++;
> - memmove(buf, c, sizeof(buf) - (c - buf));
> -
> - c = strchr(buf, ']');
> - if (!c) {
> - printf("%s: Parse failure\n", __func__);
> - exit(EXIT_FAILURE);
> - }
> - *c = '\0';
> -
> - ret = 0;
> - while (strings[ret]) {
> - if (!strcmp(strings[ret], buf))
> - return ret;
> - ret++;
> - }
> -
> - printf("Failed to parse %s\n", name);
> - exit(EXIT_FAILURE);
> -}
> -
> -static void write_string(const char *name, const char *val)
> -{
> - char path[PATH_MAX];
> - int ret;
> -
> - ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> - if (ret >= PATH_MAX) {
> - printf("%s: Pathname is too long\n", __func__);
> - exit(EXIT_FAILURE);
> - }
> -
> - if (!write_file(path, val, strlen(val) + 1)) {
> - perror(path);
> - exit(EXIT_FAILURE);
> - }
> -}
> -
> -static const unsigned long _read_num(const char *path)
> -{
> - char buf[21];
> -
> - if (read_file(path, buf, sizeof(buf)) < 0) {
> - perror("read_file(read_num)");
> - exit(EXIT_FAILURE);
> - }
> -
> - return strtoul(buf, NULL, 10);
> -}
> -
> -static const unsigned long read_num(const char *name)
> -{
> - char path[PATH_MAX];
> - int ret;
> -
> - ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> - if (ret >= PATH_MAX) {
> - printf("%s: Pathname is too long\n", __func__);
> - exit(EXIT_FAILURE);
> - }
> - return _read_num(path);
> -}
> -
> -static void _write_num(const char *path, unsigned long num)
> -{
> - char buf[21];
> -
> - sprintf(buf, "%ld", num);
> - if (!write_file(path, buf, strlen(buf) + 1)) {
> - perror(path);
> - exit(EXIT_FAILURE);
> - }
> -}
> -
> -static void write_num(const char *name, unsigned long num)
> -{
> - char path[PATH_MAX];
> - int ret;
> -
> - ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> - if (ret >= PATH_MAX) {
> - printf("%s: Pathname is too long\n", __func__);
> - exit(EXIT_FAILURE);
> - }
> - _write_num(path, num);
> -}
> -
> -static void write_settings(struct settings *settings)
> -{
> - struct khugepaged_settings *khugepaged = &settings->khugepaged;
> -
> - write_string("enabled", thp_enabled_strings[settings->thp_enabled]);
> - write_string("defrag", thp_defrag_strings[settings->thp_defrag]);
> - write_string("shmem_enabled",
> - shmem_enabled_strings[settings->shmem_enabled]);
> - write_num("use_zero_page", settings->use_zero_page);
> -
> - write_num("khugepaged/defrag", khugepaged->defrag);
> - write_num("khugepaged/alloc_sleep_millisecs",
> - khugepaged->alloc_sleep_millisecs);
> - write_num("khugepaged/scan_sleep_millisecs",
> - khugepaged->scan_sleep_millisecs);
> - write_num("khugepaged/max_ptes_none", khugepaged->max_ptes_none);
> - write_num("khugepaged/max_ptes_swap", khugepaged->max_ptes_swap);
> - write_num("khugepaged/max_ptes_shared", khugepaged->max_ptes_shared);
> - write_num("khugepaged/pages_to_scan", khugepaged->pages_to_scan);
> -
> - if (file_ops && finfo.type == VMA_FILE)
> - _write_num(finfo.dev_queue_read_ahead_path,
> - settings->read_ahead_kb);
> -}
> -
> -#define MAX_SETTINGS_DEPTH 4
> -static struct settings settings_stack[MAX_SETTINGS_DEPTH];
> -static int settings_index;
> -
> -static struct settings *current_settings(void)
> -{
> - if (!settings_index) {
> - printf("Fail: No settings set");
> - exit(EXIT_FAILURE);
> - }
> - return settings_stack + settings_index - 1;
> -}
> -
> -static void push_settings(struct settings *settings)
> -{
> - if (settings_index >= MAX_SETTINGS_DEPTH) {
> - printf("Fail: Settings stack exceeded");
> - exit(EXIT_FAILURE);
> - }
> - settings_stack[settings_index++] = *settings;
> - write_settings(current_settings());
> -}
> -
> -static void pop_settings(void)
> -{
> - if (settings_index <= 0) {
> - printf("Fail: Settings stack empty");
> - exit(EXIT_FAILURE);
> - }
> - --settings_index;
> - write_settings(current_settings());
> -}
> -
> static void restore_settings_atexit(void)
> {
> if (skip_settings_restore)
> return;
>
> printf("Restore THP and khugepaged settings...");
> - write_settings(&saved_settings);
> + thp_restore_settings();
> success("OK");
>
> skip_settings_restore = true;
> @@ -395,27 +111,9 @@ static void restore_settings(int sig)
> static void save_settings(void)
> {
> printf("Save THP and khugepaged settings...");
> - saved_settings = (struct settings) {
> - .thp_enabled = read_string("enabled", thp_enabled_strings),
> - .thp_defrag = read_string("defrag", thp_defrag_strings),
> - .shmem_enabled =
> - read_string("shmem_enabled", shmem_enabled_strings),
> - .use_zero_page = read_num("use_zero_page"),
> - };
> - saved_settings.khugepaged = (struct khugepaged_settings) {
> - .defrag = read_num("khugepaged/defrag"),
> - .alloc_sleep_millisecs =
> - read_num("khugepaged/alloc_sleep_millisecs"),
> - .scan_sleep_millisecs =
> - read_num("khugepaged/scan_sleep_millisecs"),
> - .max_ptes_none = read_num("khugepaged/max_ptes_none"),
> - .max_ptes_swap = read_num("khugepaged/max_ptes_swap"),
> - .max_ptes_shared = read_num("khugepaged/max_ptes_shared"),
> - .pages_to_scan = read_num("khugepaged/pages_to_scan"),
> - };
> if (file_ops && finfo.type == VMA_FILE)
> - saved_settings.read_ahead_kb =
> - _read_num(finfo.dev_queue_read_ahead_path);
> + thp_set_read_ahead_path(finfo.dev_queue_read_ahead_path);
> + thp_save_settings();
>
> success("OK");
>
> @@ -798,7 +496,7 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages,
> struct mem_ops *ops, bool expect)
> {
> int ret;
> - struct settings settings = *current_settings();
> + struct thp_settings settings = *thp_current_settings();
>
> printf("%s...", msg);
>
> @@ -808,7 +506,7 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages,
> */
> settings.thp_enabled = THP_NEVER;
> settings.shmem_enabled = SHMEM_NEVER;
> - push_settings(&settings);
> + thp_push_settings(&settings);
>
> /* Clear VM_NOHUGEPAGE */
> madvise(p, nr_hpages * hpage_pmd_size, MADV_HUGEPAGE);
> @@ -820,7 +518,7 @@ static void __madvise_collapse(const char *msg, char *p, int nr_hpages,
> else
> success("OK");
>
> - pop_settings();
> + thp_pop_settings();
> }
>
> static void madvise_collapse(const char *msg, char *p, int nr_hpages,
> @@ -850,13 +548,13 @@ static bool wait_for_scan(const char *msg, char *p, int nr_hpages,
> madvise(p, nr_hpages * hpage_pmd_size, MADV_HUGEPAGE);
>
> /* Wait until the second full_scan completed */
> - full_scans = read_num("khugepaged/full_scans") + 2;
> + full_scans = thp_read_num("khugepaged/full_scans") + 2;
>
> printf("%s...", msg);
> while (timeout--) {
> if (ops->check_huge(p, nr_hpages))
> break;
> - if (read_num("khugepaged/full_scans") >= full_scans)
> + if (thp_read_num("khugepaged/full_scans") >= full_scans)
> break;
> printf(".");
> usleep(TICK);
> @@ -911,11 +609,11 @@ static bool is_tmpfs(struct mem_ops *ops)
>
> static void alloc_at_fault(void)
> {
> - struct settings settings = *current_settings();
> + struct thp_settings settings = *thp_current_settings();
> char *p;
>
> settings.thp_enabled = THP_ALWAYS;
> - push_settings(&settings);
> + thp_push_settings(&settings);
>
> p = alloc_mapping(1);
> *p = 1;
> @@ -925,7 +623,7 @@ static void alloc_at_fault(void)
> else
> fail("Fail");
>
> - pop_settings();
> + thp_pop_settings();
>
> madvise(p, page_size, MADV_DONTNEED);
> printf("Split huge PMD on MADV_DONTNEED...");
> @@ -973,11 +671,11 @@ static void collapse_single_pte_entry(struct collapse_context *c, struct mem_ops
> static void collapse_max_ptes_none(struct collapse_context *c, struct mem_ops *ops)
> {
> int max_ptes_none = hpage_pmd_nr / 2;
> - struct settings settings = *current_settings();
> + struct thp_settings settings = *thp_current_settings();
> void *p;
>
> settings.khugepaged.max_ptes_none = max_ptes_none;
> - push_settings(&settings);
> + thp_push_settings(&settings);
>
> p = ops->setup_area(1);
>
> @@ -1002,7 +700,7 @@ static void collapse_max_ptes_none(struct collapse_context *c, struct mem_ops *o
> }
> skip:
> ops->cleanup_area(p, hpage_pmd_size);
> - pop_settings();
> + thp_pop_settings();
> }
>
> static void collapse_swapin_single_pte(struct collapse_context *c, struct mem_ops *ops)
> @@ -1033,7 +731,7 @@ static void collapse_swapin_single_pte(struct collapse_context *c, struct mem_op
>
> static void collapse_max_ptes_swap(struct collapse_context *c, struct mem_ops *ops)
> {
> - int max_ptes_swap = read_num("khugepaged/max_ptes_swap");
> + int max_ptes_swap = thp_read_num("khugepaged/max_ptes_swap");
> void *p;
>
> p = ops->setup_area(1);
> @@ -1250,11 +948,11 @@ static void collapse_fork_compound(struct collapse_context *c, struct mem_ops *o
> fail("Fail");
> ops->fault(p, 0, page_size);
>
> - write_num("khugepaged/max_ptes_shared", hpage_pmd_nr - 1);
> + thp_write_num("khugepaged/max_ptes_shared", hpage_pmd_nr - 1);
> c->collapse("Collapse PTE table full of compound pages in child",
> p, 1, ops, true);
> - write_num("khugepaged/max_ptes_shared",
> - current_settings()->khugepaged.max_ptes_shared);
> + thp_write_num("khugepaged/max_ptes_shared",
> + thp_current_settings()->khugepaged.max_ptes_shared);
>
> validate_memory(p, 0, hpage_pmd_size);
> ops->cleanup_area(p, hpage_pmd_size);
> @@ -1275,7 +973,7 @@ static void collapse_fork_compound(struct collapse_context *c, struct mem_ops *o
>
> static void collapse_max_ptes_shared(struct collapse_context *c, struct mem_ops *ops)
> {
> - int max_ptes_shared = read_num("khugepaged/max_ptes_shared");
> + int max_ptes_shared = thp_read_num("khugepaged/max_ptes_shared");
> int wstatus;
> void *p;
>
> @@ -1443,7 +1141,7 @@ static void parse_test_type(int argc, const char **argv)
>
> int main(int argc, const char **argv)
> {
> - struct settings default_settings = {
> + struct thp_settings default_settings = {
> .thp_enabled = THP_MADVISE,
> .thp_defrag = THP_DEFRAG_ALWAYS,
> .shmem_enabled = SHMEM_ADVISE,
> @@ -1484,7 +1182,7 @@ int main(int argc, const char **argv)
> default_settings.khugepaged.pages_to_scan = hpage_pmd_nr * 8;
>
> save_settings();
> - push_settings(&default_settings);
> + thp_push_settings(&default_settings);
>
> alloc_at_fault();
>
> diff --git a/tools/testing/selftests/mm/thp_settings.c b/tools/testing/selftests/mm/thp_settings.c
> new file mode 100644
> index 000000000000..5e8ec792cac7
> --- /dev/null
> +++ b/tools/testing/selftests/mm/thp_settings.c
> @@ -0,0 +1,296 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <fcntl.h>
> +#include <limits.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +#include "thp_settings.h"
> +
> +#define THP_SYSFS "/sys/kernel/mm/transparent_hugepage/"
> +#define MAX_SETTINGS_DEPTH 4
> +static struct thp_settings settings_stack[MAX_SETTINGS_DEPTH];
> +static int settings_index;
> +static struct thp_settings saved_settings;
> +static char dev_queue_read_ahead_path[PATH_MAX];
> +
> +static const char * const thp_enabled_strings[] = {
> + "always",
> + "madvise",
> + "never",
> + NULL
> +};
> +
> +static const char * const thp_defrag_strings[] = {
> + "always",
> + "defer",
> + "defer+madvise",
> + "madvise",
> + "never",
> + NULL
> +};
> +
> +static const char * const shmem_enabled_strings[] = {
> + "always",
> + "within_size",
> + "advise",
> + "never",
> + "deny",
> + "force",
> + NULL
> +};
> +
> +int read_file(const char *path, char *buf, size_t buflen)
> +{
> + int fd;
> + ssize_t numread;
> +
> + fd = open(path, O_RDONLY);
> + if (fd == -1)
> + return 0;
> +
> + numread = read(fd, buf, buflen - 1);
> + if (numread < 1) {
> + close(fd);
> + return 0;
> + }
> +
> + buf[numread] = '\0';
> + close(fd);
> +
> + return (unsigned int) numread;
> +}
> +
> +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) {
> + printf("open(%s)\n", path);
> + exit(EXIT_FAILURE);
> + return 0;
> + }
> +
> + numwritten = write(fd, buf, buflen - 1);
> + close(fd);
> + if (numwritten < 1) {
> + printf("write(%s)\n", buf);
> + exit(EXIT_FAILURE);
> + return 0;
> + }
> +
> + return (unsigned int) numwritten;
> +}
> +
> +const unsigned long read_num(const char *path)
> +{
> + char buf[21];
> +
> + if (read_file(path, buf, sizeof(buf)) < 0) {
> + perror("read_file()");
> + exit(EXIT_FAILURE);
> + }
> +
> + return strtoul(buf, NULL, 10);
> +}
> +
> +void write_num(const char *path, unsigned long num)
> +{
> + char buf[21];
> +
> + sprintf(buf, "%ld", num);
> + if (!write_file(path, buf, strlen(buf) + 1)) {
> + perror(path);
> + exit(EXIT_FAILURE);
> + }
> +}
> +
> +int thp_read_string(const char *name, const char * const strings[])
> +{
> + char path[PATH_MAX];
> + char buf[256];
> + char *c;
> + int ret;
> +
> + ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> + if (ret >= PATH_MAX) {
> + printf("%s: Pathname is too long\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> +
> + if (!read_file(path, buf, sizeof(buf))) {
> + perror(path);
> + exit(EXIT_FAILURE);
> + }
> +
> + c = strchr(buf, '[');
> + if (!c) {
> + printf("%s: Parse failure\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> +
> + c++;
> + memmove(buf, c, sizeof(buf) - (c - buf));
> +
> + c = strchr(buf, ']');
> + if (!c) {
> + printf("%s: Parse failure\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> + *c = '\0';
> +
> + ret = 0;
> + while (strings[ret]) {
> + if (!strcmp(strings[ret], buf))
> + return ret;
> + ret++;
> + }
> +
> + printf("Failed to parse %s\n", name);
> + exit(EXIT_FAILURE);
> +}
> +
> +void thp_write_string(const char *name, const char *val)
> +{
> + char path[PATH_MAX];
> + int ret;
> +
> + ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> + if (ret >= PATH_MAX) {
> + printf("%s: Pathname is too long\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> +
> + if (!write_file(path, val, strlen(val) + 1)) {
> + perror(path);
> + exit(EXIT_FAILURE);
> + }
> +}
> +
> +const unsigned long thp_read_num(const char *name)
> +{
> + char path[PATH_MAX];
> + int ret;
> +
> + ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> + if (ret >= PATH_MAX) {
> + printf("%s: Pathname is too long\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> + return read_num(path);
> +}
> +
> +void thp_write_num(const char *name, unsigned long num)
> +{
> + char path[PATH_MAX];
> + int ret;
> +
> + ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
> + if (ret >= PATH_MAX) {
> + printf("%s: Pathname is too long\n", __func__);
> + exit(EXIT_FAILURE);
> + }
> + write_num(path, num);
> +}
> +
> +void thp_read_settings(struct thp_settings *settings)
> +{
> + *settings = (struct thp_settings) {
> + .thp_enabled = thp_read_string("enabled", thp_enabled_strings),
> + .thp_defrag = thp_read_string("defrag", thp_defrag_strings),
> + .shmem_enabled =
> + thp_read_string("shmem_enabled", shmem_enabled_strings),
> + .use_zero_page = thp_read_num("use_zero_page"),
> + };
> + settings->khugepaged = (struct khugepaged_settings) {
> + .defrag = thp_read_num("khugepaged/defrag"),
> + .alloc_sleep_millisecs =
> + thp_read_num("khugepaged/alloc_sleep_millisecs"),
> + .scan_sleep_millisecs =
> + thp_read_num("khugepaged/scan_sleep_millisecs"),
> + .max_ptes_none = thp_read_num("khugepaged/max_ptes_none"),
> + .max_ptes_swap = thp_read_num("khugepaged/max_ptes_swap"),
> + .max_ptes_shared = thp_read_num("khugepaged/max_ptes_shared"),
> + .pages_to_scan = thp_read_num("khugepaged/pages_to_scan"),
> + };
> + if (dev_queue_read_ahead_path[0])
> + settings->read_ahead_kb = read_num(dev_queue_read_ahead_path);
> +}
> +
> +void thp_write_settings(struct thp_settings *settings)
> +{
> + struct khugepaged_settings *khugepaged = &settings->khugepaged;
> +
> + thp_write_string("enabled", thp_enabled_strings[settings->thp_enabled]);
> + thp_write_string("defrag", thp_defrag_strings[settings->thp_defrag]);
> + thp_write_string("shmem_enabled",
> + shmem_enabled_strings[settings->shmem_enabled]);
> + thp_write_num("use_zero_page", settings->use_zero_page);
> +
> + thp_write_num("khugepaged/defrag", khugepaged->defrag);
> + thp_write_num("khugepaged/alloc_sleep_millisecs",
> + khugepaged->alloc_sleep_millisecs);
> + thp_write_num("khugepaged/scan_sleep_millisecs",
> + khugepaged->scan_sleep_millisecs);
> + thp_write_num("khugepaged/max_ptes_none", khugepaged->max_ptes_none);
> + thp_write_num("khugepaged/max_ptes_swap", khugepaged->max_ptes_swap);
> + thp_write_num("khugepaged/max_ptes_shared", khugepaged->max_ptes_shared);
> + thp_write_num("khugepaged/pages_to_scan", khugepaged->pages_to_scan);
> +
> + if (dev_queue_read_ahead_path[0])
> + write_num(dev_queue_read_ahead_path, settings->read_ahead_kb);
> +}
> +
> +struct thp_settings *thp_current_settings(void)
> +{
> + if (!settings_index) {
> + printf("Fail: No settings set");
> + exit(EXIT_FAILURE);
> + }
> + return settings_stack + settings_index - 1;
> +}
> +
> +void thp_push_settings(struct thp_settings *settings)
> +{
> + if (settings_index >= MAX_SETTINGS_DEPTH) {
> + printf("Fail: Settings stack exceeded");
> + exit(EXIT_FAILURE);
> + }
> + settings_stack[settings_index++] = *settings;
> + thp_write_settings(thp_current_settings());
> +}
> +
> +void thp_pop_settings(void)
> +{
> + if (settings_index <= 0) {
> + printf("Fail: Settings stack empty");
> + exit(EXIT_FAILURE);
> + }
> + --settings_index;
> + thp_write_settings(thp_current_settings());
> +}
> +
> +void thp_restore_settings(void)
> +{
> + thp_write_settings(&saved_settings);
> +}
> +
> +void thp_save_settings(void)
> +{
> + thp_read_settings(&saved_settings);
> +}
> +
> +void thp_set_read_ahead_path(char *path)
> +{
> + if (!path) {
> + dev_queue_read_ahead_path[0] = '\0';
> + return;
> + }
> +
> + strncpy(dev_queue_read_ahead_path, path,
> + sizeof(dev_queue_read_ahead_path));
> + dev_queue_read_ahead_path[sizeof(dev_queue_read_ahead_path) - 1] = '\0';
> +}
> diff --git a/tools/testing/selftests/mm/thp_settings.h b/tools/testing/selftests/mm/thp_settings.h
> new file mode 100644
> index 000000000000..ff3d98c30617
> --- /dev/null
> +++ b/tools/testing/selftests/mm/thp_settings.h
> @@ -0,0 +1,71 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __THP_SETTINGS_H__
> +#define __THP_SETTINGS_H__
> +
> +#include <stdbool.h>
> +#include <stddef.h>
> +#include <stdint.h>
> +
> +enum thp_enabled {
> + THP_ALWAYS,
> + THP_MADVISE,
> + THP_NEVER,
> +};
> +
> +enum thp_defrag {
> + THP_DEFRAG_ALWAYS,
> + THP_DEFRAG_DEFER,
> + THP_DEFRAG_DEFER_MADVISE,
> + THP_DEFRAG_MADVISE,
> + THP_DEFRAG_NEVER,
> +};
> +
> +enum shmem_enabled {
> + SHMEM_ALWAYS,
> + SHMEM_WITHIN_SIZE,
> + SHMEM_ADVISE,
> + SHMEM_NEVER,
> + SHMEM_DENY,
> + SHMEM_FORCE,
> +};
> +
> +struct khugepaged_settings {
> + bool defrag;
> + unsigned int alloc_sleep_millisecs;
> + unsigned int scan_sleep_millisecs;
> + unsigned int max_ptes_none;
> + unsigned int max_ptes_swap;
> + unsigned int max_ptes_shared;
> + unsigned long pages_to_scan;
> +};
> +
> +struct thp_settings {
> + enum thp_enabled thp_enabled;
> + enum thp_defrag thp_defrag;
> + enum shmem_enabled shmem_enabled;
> + bool use_zero_page;
> + struct khugepaged_settings khugepaged;
> + unsigned long read_ahead_kb;
> +};
> +
> +int read_file(const char *path, char *buf, size_t buflen);
> +int write_file(const char *path, const char *buf, size_t buflen);
> +const unsigned long read_num(const char *path);
> +void write_num(const char *path, unsigned long num);
> +
> +int thp_read_string(const char *name, const char * const strings[]);
> +void thp_write_string(const char *name, const char *val);
> +const unsigned long thp_read_num(const char *name);
> +void thp_write_num(const char *name, unsigned long num);
> +
> +void thp_write_settings(struct thp_settings *settings);
> +void thp_read_settings(struct thp_settings *settings);
> +struct thp_settings *thp_current_settings(void);
> +void thp_push_settings(struct thp_settings *settings);
> +void thp_pop_settings(void);
> +void thp_restore_settings(void);
> +void thp_save_settings(void);
> +
> +void thp_set_read_ahead_path(char *path);
> +
> +#endif /* __THP_SETTINGS_H__ */
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