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 28%, and write
for 14% on Intel ICX 160 cores configuration with v6.8-rc6.
Reviewed-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Signed-off-by: Yu Ma <yu.ma@xxxxxxxxx>
---
fs/file.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/file.c b/fs/file.c
index e8d2f9ef7fd1..a0e94a178c0b 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 unsigned int count_open_files(struct fdtable *fdt)
--
2.43.0
