From: Yu Ma <yu.ma@xxxxxxxxx>
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.
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@xxxxxxx>
Reviewed-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Signed-off-by: Yu Ma <yu.ma@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240717145018.3972922-3-yu.ma@xxxxxxxxx
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/file.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/file.c b/fs/file.c
index 9b8df3bc6fea..d6f5add1a786 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -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)
--
2.39.2
