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

Ma, Yu
2024-06-25T15:41:36Z

On 6/25/2024 7:54 PM, Jan Kara wrote:
> 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

Copy that, thanks 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
>>