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fs/file.c: conditionally clear full_fds

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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 fc90888d07
("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: Jan Kara <jack@suse.cz>
Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Yu Ma <yu.ma@intel.com>
Link: https://lore.kernel.org/r/20240717145018.3972922-3-yu.ma@intel.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Yu Ma 2024-07-17 10:50:17 -04:00 • committed by Al Viro
parent 52732bb9ab
commit c9a3019603
1 changed files with 3 additions and 1 deletions
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4
fs/file.c
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@ -264,7 +264,9 @@ 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);
}
static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)