Commit 3f60bf6a authored by Yu Ma's avatar Yu Ma Committed by Zheng Zengkai
Browse files

fs/file.c: conditionally clear full_fds 

mainline inclusion
from mainline-v6.12-rc3
commit c9a3019603b8a8519f1b6d8ae0059bcb2965f8fe
category: performance
bugzilla: https://gitee.com/openeuler/kernel/issues/IB8ROX
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c9a3019603b8a8519f1b6d8ae0059bcb2965f8fe



-------------------------------------------------

64 bits in open_fds are mapped to a common bit in full_fds_bits. It is very
likely that a bit in full_fds_bits has been cleared before in
__clear_open_fds()'s operation. Check the clear bit in full_fds_bits before
clearing to avoid unnecessary write and cache bouncing. See commit fc90888d
("vfs: conditionally clear close-on-exec flag") for a similar optimization.
take stock kernel with patch 1 as baseline, it improves pts/blogbench-1.1.0
read for 13%, and write for 5% on Intel ICX 160 cores configuration with
v6.10-rc7.

Reviewed-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: default avatarYu Ma <yu.ma@intel.com>
Link: https://lore.kernel.org/r/20240717145018.3972922-3-yu.ma@intel.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 3b393e43

fs/file.c

+3 −1
Original line number Diff line number Diff line
@@ -265,7 +265,9 @@ static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt) 
static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)

{

	__clear_bit(fd, fdt->open_fds);

	__clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);

	fd /= BITS_PER_LONG;

	if (test_bit(fd, fdt->full_fds_bits))

		__clear_bit(fd, fdt->full_fds_bits);

}



/*