Linus Torvalds 9013c51c63 vfs: mostly undo glibc turning 'fstat()' into 'fstatat(AT_EMPTY_PATH)' ... Mateusz reports that glibc turns 'fstat()' calls into 'fstatat()', and that seems to have been going on for quite a long time due to glibc having tried to simplify its stat logic into just one point. This turns out to cause completely unnecessary overhead, where we then go off and allocate the kernel side pathname, and actually look up the empty path. Sure, our path lookup is quite optimized, but it still causes a fair bit of allocation overhead and a couple of completely unnecessary rounds of lockref accesses etc. This is all hopefully getting fixed in user space, and there is a patch floating around for just having glibc use the native fstat() system call. But even with the current situation we can at least improve on things by catching the situation and short-circuiting it. Note that this is still measurably slower than just a plain 'fstat()', since just checking that the filename is actually empty is somewhat expensive due to inevitable user space access overhead from the kernel (ie verifying pointers, and SMAP on x86). But it's still quite a bit faster than actually looking up the path for real. To quote numers from Mateusz: "Sapphire Rapids, will-it-scale, ops/s stock fstat 5088199 patched fstat 7625244 (+49%) real fstat 8540383 (+67% / +12%)" where that 'stock fstat' is the glibc translation of fstat into fstatat() with an empty path, the 'patched fstat' is with this short circuiting of the path lookup, and the 'real fstat' is the actual native fstat() system call with none of this overhead. Link: https://lore.kernel.org/lkml/20230903204858.lv7i3kqvw6eamhgz@f/ Reported-by: Mateusz Guzik <mjguzik@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2023-09-07 09:40:30 -07:00
..
9p	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
adfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
affs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
afs	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
autofs	v6.6-vfs.autofs	2023-08-28 11:39:14 -07:00
befs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
bfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
btrfs	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
cachefiles	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
ceph	Mixed with some fixes and cleanups, this brings in reasonably complete	2023-09-06 12:10:15 -07:00
coda	v6.6-vfs.ctime	2023-08-28 09:31:32 -07:00
configfs	configfs: convert to ctime accessor functions	2023-07-13 10:28:05 +02:00
cramfs	v6.6-vfs.super	2023-08-28 11:04:18 -07:00
crypto
debugfs	Char/Misc driver changes for 6.6-rc1	2023-09-01 09:53:54 -07:00
devpts	v6.6-vfs.misc	2023-08-28 10:17:14 -07:00
dlm	dlm: fix plock lookup when using multiple lockspaces	2023-08-25 10:31:39 -05:00
ecryptfs	v6.6-vfs.misc	2023-08-28 10:17:14 -07:00
efivarfs	efivarfs: convert to ctime accessor functions	2023-07-13 10:28:06 +02:00
efs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
erofs	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
exfat	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
exportfs	exportfs: remove kernel-doc warnings in exportfs	2023-08-29 17:45:22 -04:00
ext2	\n	2023-08-30 12:10:50 -07:00
ext4	Many ext4 and jbd2 cleanups and bug fixes for v6.6-rc1.	2023-08-31 15:18:15 -07:00
f2fs	f2fs update for 6.6-rc1	2023-09-02 15:37:59 -07:00
fat	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
freevxfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
fscache
fuse	fuse update for 6.6	2023-09-05 12:45:55 -07:00
gfs2	gfs2 fixes	2023-09-05 13:00:28 -07:00
hfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
hfsplus	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
hostfs	hostfs: convert to ctime accessor functions	2023-07-24 10:30:00 +02:00
hpfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
hugetlbfs	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
iomap	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
isofs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
jbd2	Many ext4 and jbd2 cleanups and bug fixes for v6.6-rc1.	2023-08-31 15:18:15 -07:00
jffs2	jffs2: convert to ctime accessor functions	2023-07-24 10:30:01 +02:00
jfs	A few small fixes	2023-08-31 15:25:01 -07:00
kernfs	Driver core changes for 6.6-rc1	2023-09-01 09:43:18 -07:00
lockd	SUNRPC: Add enum svc_auth_status	2023-08-29 17:45:22 -04:00
minix	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
netfs
nfs	NFS CLient Updates for Linux 6.6	2023-08-31 15:36:41 -07:00
nfs_common
nfsd	NFSD 6.6 Release Notes	2023-08-31 15:32:18 -07:00
nilfs2	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
nls	fs/jfs: Use common ucs2 upper case table	2023-08-30 08:55:52 -05:00
notify	dnotify: Pass argument of fcntl_dirnotify as int	2023-07-10 14:36:12 +02:00
ntfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
ntfs3	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
ocfs2	Many ext4 and jbd2 cleanups and bug fixes for v6.6-rc1.	2023-08-31 15:18:15 -07:00
omfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
openpromfs	openpromfs: convert to ctime accessor functions	2023-07-24 10:30:03 +02:00
orangefs	fs: drop the timespec64 argument from update_time	2023-08-11 09:04:57 +02:00
overlayfs	overlayfs update for 6.6	2023-08-30 11:54:09 -07:00
proc	- Stefan Roesch has added ksm statistics to /proc/pid/smaps	2023-09-05 10:56:27 -07:00
pstore	pstore fix for v6.6-rc1	2023-09-02 10:45:17 -07:00
qnx4	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
qnx6	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
quota	\n	2023-08-30 12:10:50 -07:00
ramfs	ramfs: convert to ctime accessor functions	2023-07-24 10:30:04 +02:00
reiserfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
romfs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
smb	ten ksmbd server fixes	2023-08-31 15:28:26 -07:00
squashfs	squashfs: convert to ctime accessor functions	2023-07-24 10:30:05 +02:00
sysfs
sysv	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
tracefs	Tracing updates for 6.6:	2023-09-01 16:34:25 -07:00
ubifs	fs: drop the timespec64 argument from update_time	2023-08-11 09:04:57 +02:00
udf	\n	2023-08-30 12:10:50 -07:00
ufs	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
unicode
vboxsf	v6.6-vfs.ctime	2023-08-28 09:31:32 -07:00
verity	fsverity: skip PKCS#7 parser when keyring is empty	2023-08-20 10:33:43 -07:00
xfs	New code for 6.6:	2023-08-30 12:34:12 -07:00
zonefs	New code for 6.6:	2023-08-28 11:59:52 -07:00
aio.c	Add x86 shadow stack support	2023-08-31 12:20:12 -07:00
anon_inodes.c
attr.c	v6.6-vfs.misc	2023-08-28 10:17:14 -07:00
bad_inode.c	fs: drop the timespec64 argument from update_time	2023-08-11 09:04:57 +02:00
binfmt_elf_fdpic.c	binfmt_elf_fdpic: support 64-bit systems	2023-08-23 14:17:42 -07:00
binfmt_elf_test.c
binfmt_elf.c	Merge branch 'expand-stack'	2023-06-28 20:35:21 -07:00
binfmt_flat.c
binfmt_misc.c	fs: convert to ctime accessor functions	2023-07-13 10:28:04 +02:00
binfmt_script.c
buffer.c	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
char_dev.c
compat_binfmt_elf.c
coredump.c	v6.5/vfs.misc	2023-06-26 09:50:21 -07:00
d_path.c
dax.c	mm: remove enum page_entry_size	2023-08-24 16:20:30 -07:00
dcache.c	fs/dcache: Replace printk and WARN_ON by WARN	2023-08-19 13:41:11 +02:00
direct-io.c	- Yosry Ahmed brought back some cgroup v1 stats in OOM logs.	2023-06-28 10:28:11 -07:00
drop_caches.c	fs: drop_caches: draining pages before dropping caches	2023-08-18 10:12:11 -07:00
eventfd.c	eventfd: prevent underflow for eventfd semaphores	2023-07-11 11:41:34 +02:00
eventpoll.c	epoll: simplify ep_alloc()	2023-07-26 14:56:07 +02:00
exec.c	- An extensive rework of kexec and crash Kconfig from Eric DeVolder	2023-08-29 14:53:51 -07:00
fcntl.c	fcntl: Cast commands with int args explicitly	2023-07-10 14:36:11 +02:00
fhandle.c
file_table.c	fs: use __fput_sync in close(2)	2023-08-08 19:36:51 +02:00
file.c	v6.6-vfs.misc	2023-08-28 10:17:14 -07:00
filesystems.c
fs_context.c	v6.6-vfs.misc	2023-08-28 10:17:14 -07:00
fs_parser.c
fs_pin.c
fs_struct.c	kill do_each_thread()	2023-08-21 13:46:25 -07:00
fs_types.c
fs-writeback.c	super: make locking naming consistent	2023-08-21 14:36:57 +02:00
fsopen.c	fs: add FSCONFIG_CMD_CREATE_EXCL	2023-08-14 18:48:02 +02:00
init.c
inode.c	v6.6-vfs.super	2023-08-28 11:04:18 -07:00
internal.h	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
ioctl.c	v6.6-vfs.super	2023-08-28 11:04:18 -07:00
Kconfig	for-6.6/block-2023-08-28	2023-08-29 20:21:42 -07:00
Kconfig.binfmt	riscv: support the elf-fdpic binfmt loader	2023-08-23 14:17:43 -07:00
kernel_read_file.c	fs: Fix kernel-doc warnings	2023-08-19 12:12:12 +02:00
libfs.c	Many ext4 and jbd2 cleanups and bug fixes for v6.6-rc1.	2023-08-31 15:18:15 -07:00
locks.c	NFSD 6.6 Release Notes	2023-08-31 15:32:18 -07:00
Makefile	fs: add CONFIG_BUFFER_HEAD	2023-08-02 09:13:09 -06:00
mbcache.c
mnt_idmapping.c
mount.h
mpage.c
namei.c	fs: Fix kernel-doc warnings	2023-08-19 12:12:12 +02:00
namespace.c	v6.5/vfs.mount	2023-06-26 10:27:04 -07:00
nsfs.c	fs: convert to ctime accessor functions	2023-07-13 10:28:04 +02:00
open.c	v6.6-vfs.fchmodat2	2023-08-28 11:25:27 -07:00
pipe.c	v6.6-vfs.misc	2023-08-28 10:17:14 -07:00
pnode.c
pnode.h
posix_acl.c	fs: convert to ctime accessor functions	2023-07-13 10:28:04 +02:00
proc_namespace.c
read_write.c	fs: Fix one kernel-doc comment	2023-08-15 08:32:45 +02:00
readdir.c	vfs: get rid of old '->iterate' directory operation	2023-08-06 15:08:35 +02:00
remap_range.c
select.c
seq_file.c
signalfd.c
splice.c	- Some swap cleanups from Ma Wupeng ("fix WARN_ON in add_to_avail_list")	2023-08-29 14:25:26 -07:00
stack.c	fs: convert to ctime accessor functions	2023-07-13 10:28:04 +02:00
stat.c	vfs: mostly undo glibc turning 'fstat()' into 'fstatat(AT_EMPTY_PATH)'	2023-09-07 09:40:30 -07:00
statfs.c
super.c	fs: export sget_dev()	2023-08-31 12:47:15 +02:00
sync.c
sysctls.c
timerfd.c
userfaultfd.c	mm: userfaultfd: remove stale comment about core dump locking	2023-08-24 16:20:27 -07:00
utimes.c
xattr.c	tmpfs,xattr: GFP_KERNEL_ACCOUNT for simple xattrs	2023-08-22 10:57:46 +02:00