Speeds up generic_file_write() by not calling mark_inode_dirty() when
the mtime and ctime didn't change.
There may be concerns over the fact that this restricts mtime and ctime
updates to one-second resolution. But the interface doesn't support
that anyway - all the filesystem knows is that its dirty_inode()
superop was called. It doesn't know why.
So filesystems which support high-resolution timestamps already need to
make their own arrangements. We need an update_mtime i_op to support
those properly.
time to write a one megabyte file one-byte-at-a-time:
Before:
ext3: 24.8 seconds
ext2: 4.9 seconds
reiserfs: 17.0 seconds
After:
ext3: 22.5 seconds
ext2: 4.8 seconds
reiserfs: 11.6 seconds
Not much improvement because we're also calling expensive
mark_inode_dirty() functions when i_size is expanded. So compare the
overwrite case:
time dd if=/dev/zero of=foo bs=1 count=1M conv=notrunc
ext3 before: 20.0 seconds
ext3 after: 9.7 seconds
=====================================
--- 2.5.19/mm/filemap.c~mtime-speedup Sat Jun 1 01:18:08 2002
+++ 2.5.19-akpm/mm/filemap.c Sat Jun 1 01:18:08 2002
@@ -2098,6 +2098,7 @@ generic_file_write(struct file *file, co
ssize_t written;
int err;
unsigned bytes;
+ time_t time_now;
if (unlikely((ssize_t) count < 0))
return -EINVAL;
@@ -2195,9 +2196,12 @@ generic_file_write(struct file *file, co
goto out;
remove_suid(file->f_dentry);
- inode->i_ctime = CURRENT_TIME;
- inode->i_mtime = CURRENT_TIME;
- mark_inode_dirty_sync(inode);
+ time_now = CURRENT_TIME;
+ if (inode->i_ctime != time_now || inode->i_mtime != time_now) {
+ inode->i_ctime = time_now;
+ inode->i_mtime = time_now;
+ mark_inode_dirty_sync(inode);
+ }
if (unlikely(file->f_flags & O_DIRECT)) {
written = generic_file_direct_IO(WRITE, file,
-
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Jun 07 2002 - 22:00:10 EST