fs/file.c: conditionally clear full_fds

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 fc90888 ("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 <[email protected]> Reviewed-by: Tim Chen <[email protected]> Signed-off-by: Yu Ma <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Christian Brauner <[email protected]> Signed-off-by: Al Viro <[email protected]> (cherry picked from commit c9a3019603b8a8519f1b6d8ae0059bcb2965f8fe)
deepin-community · Jan 17, 2025 · a643cb8 · a643cb8
1 parent 7f9a1d7
commit a643cb8
Showing 1 changed file with 3 additions and 1 deletion.
diff --git 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);
 }
 
 /*