Re: [PATCH v2 2/3] fs/file.c: conditionally clear full_fds

Jan Kara
2024-06-25T11:54:48Z

On Sat 22-06-24 11:49:03, Yu Ma wrote:
> 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 fc90888d07b8
> ("vfs: conditionally clear close-on-exec flag") for a similar optimization.
> Together with patch 1, they improves pts/blogbench-1.1.0 read for 27%, and write
> for 14% on Intel ICX 160 cores configuration with v6.10-rc4.
>
> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>
> Signed-off-by: Yu Ma <yu.ma@intel.com>

Nice. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/file.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/file.c b/fs/file.c
> index 50e900a47107..b4d25f6d4c19 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -268,7 +268,9 @@ 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)
> --
> 2.43.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR