The patch titled
Subject: shmem: avoid huge pages for small files
has been added to the -mm tree. Its filename is
shmem-avoid-huge-pages-for-small-files.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/shmem-avoid-huge-pages-for-small-files.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/shmem-avoid-huge-pages-for-small-files.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: shmem: avoid huge pages for small files
Huge pages are detrimental for small file: they causes noticible overhead
on both allocation performance and memory footprint.
This patch aimed to address this issue by avoiding huge pages until file
grown to specified size. This would cover most of the cases where huge
pages causes regressions in performance.
By default the minimal file size to allocate huge pages is equal to size
of huge page.
Depending on how well CPU microarchitecture deals with huge pages, you
might need to set it higher in order to balance out overhead with benefit
of huge pages.
In other case, if it's known in advance that specific mount would be
populated with large files, you might want to set it to zero to get huge
pages allocated from the beginning.
We add two handle to specify minimal file size for huge pages:
- mount option 'huge_min_size';
- sysfs file /sys/kernel/mm/transparent_hugepage/shmem_min_size for
in-kernel tmpfs mount;
Few notes:
- if shmem_enabled is set to 'force', the limit is ignored. We still
want to generate as many pages as possible for functional testing.
- the limit doesn't affect khugepaged behaviour: it still can collapse
pages based on its settings;
- remount of the filesystem doesn't affect previously allocated pages,
but the limit is applied for new allocations;
Link: http://lkml.kernel.org/r/20161018090236.183045-1-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/transhuge.txt | 6 +++
include/linux/huge_mm.h | 1
include/linux/shmem_fs.h | 1
mm/huge_memory.c | 1
mm/shmem.c | 56 ++++++++++++++++++++++++++++---
5 files changed, 60 insertions(+), 5 deletions(-)
diff -puN Documentation/vm/transhuge.txt~shmem-avoid-huge-pages-for-small-files Documentation/vm/transhuge.txt
--- a/Documentation/vm/transhuge.txt~shmem-avoid-huge-pages-for-small-files
+++ a/Documentation/vm/transhuge.txt
@@ -238,6 +238,12 @@ values:
- "force":
Force the huge option on for all - very useful for testing;
+There's limit on minimal file size before kernel starts allocate huge
+pages for it. By default it's size of huge page.
+
+You can adjust the limit using "huge_min_size=" mount option or
+/sys/kernel/mm/transparent_hugepage/shmem_min_size for in-kernel mount.
+
== Need of application restart ==
The transparent_hugepage/enabled values and tmpfs mount option only affect
diff -puN include/linux/huge_mm.h~shmem-avoid-huge-pages-for-small-files include/linux/huge_mm.h
--- a/include/linux/huge_mm.h~shmem-avoid-huge-pages-for-small-files
+++ a/include/linux/huge_mm.h
@@ -52,6 +52,7 @@ extern ssize_t single_hugepage_flag_show
struct kobj_attribute *attr, char *buf,
enum transparent_hugepage_flag flag);
extern struct kobj_attribute shmem_enabled_attr;
+extern struct kobj_attribute shmem_min_size_attr;
#define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)
diff -puN include/linux/shmem_fs.h~shmem-avoid-huge-pages-for-small-files include/linux/shmem_fs.h
--- a/include/linux/shmem_fs.h~shmem-avoid-huge-pages-for-small-files
+++ a/include/linux/shmem_fs.h
@@ -31,6 +31,7 @@ struct shmem_sb_info {
spinlock_t stat_lock; /* Serialize shmem_sb_info changes */
umode_t mode; /* Mount mode for root directory */
unsigned char huge; /* Whether to try for hugepages */
+ loff_t huge_min_size; /* No hugepages if i_size less than this */
kuid_t uid; /* Mount uid for root directory */
kgid_t gid; /* Mount gid for root directory */
struct mempolicy *mpol; /* default memory policy for mappings */
diff -puN mm/huge_memory.c~shmem-avoid-huge-pages-for-small-files mm/huge_memory.c
--- a/mm/huge_memory.c~shmem-avoid-huge-pages-for-small-files
+++ a/mm/huge_memory.c
@@ -309,6 +309,7 @@ static struct attribute *hugepage_attr[]
&use_zero_page_attr.attr,
#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
&shmem_enabled_attr.attr,
+ &shmem_min_size_attr.attr,
#endif
#ifdef CONFIG_DEBUG_VM
&debug_cow_attr.attr,
diff -puN mm/shmem.c~shmem-avoid-huge-pages-for-small-files mm/shmem.c
--- a/mm/shmem.c~shmem-avoid-huge-pages-for-small-files
+++ a/mm/shmem.c
@@ -369,6 +369,7 @@ static bool shmem_confirm_swap(struct ad
/* ifdef here to avoid bloating shmem.o when not necessary */
int shmem_huge __read_mostly;
+unsigned long long shmem_huge_min_size __read_mostly = HPAGE_PMD_SIZE;
static int shmem_parse_huge(const char *str)
{
@@ -1668,6 +1669,8 @@ repeat:
swap_free(swap);
} else {
+ loff_t i_size;
+
/* shmem_symlink() */
if (mapping->a_ops != &shmem_aops)
goto alloc_nohuge;
@@ -1675,14 +1678,17 @@ repeat:
goto alloc_nohuge;
if (shmem_huge == SHMEM_HUGE_FORCE)
goto alloc_huge;
+ i_size = i_size_read(inode);
+ if (i_size < sbinfo->huge_min_size &&
+ index < (sbinfo->huge_min_size >> PAGE_SHIFT))
+ goto alloc_nohuge;
switch (sbinfo->huge) {
- loff_t i_size;
pgoff_t off;
case SHMEM_HUGE_NEVER:
goto alloc_nohuge;
case SHMEM_HUGE_WITHIN_SIZE:
off = round_up(index, HPAGE_PMD_NR);
- i_size = round_up(i_size_read(inode), PAGE_SIZE);
+ i_size = round_up(i_size, PAGE_SIZE);
if (i_size >= HPAGE_PMD_SIZE &&
i_size >> PAGE_SHIFT >= off)
goto alloc_huge;
@@ -3349,6 +3355,10 @@ static int shmem_parse_options(char *opt
huge != SHMEM_HUGE_NEVER)
goto bad_val;
sbinfo->huge = huge;
+ } else if (!strcmp(this_char, "huge_min_size")) {
+ sbinfo->huge_min_size = memparse(value, &rest);
+ if (*rest)
+ goto bad_val;
#endif
#ifdef CONFIG_NUMA
} else if (!strcmp(this_char,"mpol")) {
@@ -3382,6 +3392,8 @@ static int shmem_remount_fs(struct super
int error = -EINVAL;
config.mpol = NULL;
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+ config.huge_min_size = HPAGE_PMD_SIZE;
if (shmem_parse_options(data, &config, true))
return error;
@@ -3403,6 +3415,7 @@ static int shmem_remount_fs(struct super
error = 0;
sbinfo->huge = config.huge;
+ sbinfo->huge_min_size = config.huge_min_size;
sbinfo->max_blocks = config.max_blocks;
sbinfo->max_inodes = config.max_inodes;
sbinfo->free_inodes = config.max_inodes - inodes;
@@ -3438,8 +3451,10 @@ static int shmem_show_options(struct seq
from_kgid_munged(&init_user_ns, sbinfo->gid));
#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
/* Rightly or wrongly, show huge mount option unmasked by shmem_huge */
- if (sbinfo->huge)
+ if (sbinfo->huge) {
seq_printf(seq, ",huge=%s", shmem_format_huge(sbinfo->huge));
+ seq_printf(seq, ",huge_min_size=%llu", sbinfo->huge_min_size);
+ }
#endif
shmem_show_mpol(seq, sbinfo->mpol);
return 0;
@@ -3542,6 +3557,8 @@ int shmem_fill_super(struct super_block
sbinfo->mode = S_IRWXUGO | S_ISVTX;
sbinfo->uid = current_fsuid();
sbinfo->gid = current_fsgid();
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
+ sbinfo->huge_min_size = HPAGE_PMD_SIZE;
sb->s_fs_info = sbinfo;
#ifdef CONFIG_TMPFS
@@ -3780,9 +3797,10 @@ int __init shmem_init(void)
}
#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
- if (has_transparent_hugepage() && shmem_huge < SHMEM_HUGE_DENY)
+ if (has_transparent_hugepage() && shmem_huge < SHMEM_HUGE_DENY) {
SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
- else
+ SHMEM_SB(shm_mnt->mnt_sb)->huge_min_size = shmem_huge_min_size;
+ } else
shmem_huge = 0; /* just in case it was patched */
#endif
return 0;
@@ -3848,6 +3866,34 @@ static ssize_t shmem_enabled_store(struc
struct kobj_attribute shmem_enabled_attr =
__ATTR(shmem_enabled, 0644, shmem_enabled_show, shmem_enabled_store);
+
+static ssize_t shmem_min_size_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%llu\n", shmem_huge_min_size);
+}
+
+
+static ssize_t shmem_min_size_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ unsigned long long size;
+ char *end;
+
+ size = memparse(buf, &end);
+ if (end == buf)
+ return -EINVAL;
+ if (*end == '\n')
+ end++;
+ if (*end != '\0')
+ return -EINVAL;
+ shmem_huge_min_size = size;
+ SHMEM_SB(shm_mnt->mnt_sb)->huge_min_size = size;
+ return end - buf;
+}
+
+struct kobj_attribute shmem_min_size_attr =
+ __ATTR(shmem_min_size, 0644, shmem_min_size_show, shmem_min_size_store);
#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE && CONFIG_SYSFS */
#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
shmem-avoid-huge-pages-for-small-files.patch
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