Message-ID: <2eeae472-3c01-4646-9eca-bfb9733692c7@arm.com>
Date:   Mon, 27 Nov 2023 12:22:39 +0000
From:   Ryan Roberts <ryan.roberts@....com>
To:     Alistair Popple <apopple@...dia.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

On 23/11/2023 06:07, Alistair Popple wrote:
> 
> 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>

Thanks! Its pretty much just a cut-and-paste; I did prefix the function names
with "thp_" since they are now in global namespace. And I moved some khugepaged
test-specific logging out of them and into the higher level test code. And I
added thp_set_read_ahead_path() to decouple from the test code. But intended to
all be equivalent.

> 
>> ---
>>  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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