[ Al Viro added to Cc: as the arbiter of good taste in the VFS layer. He
has veto powers even over my proposals ;^]
On Tue, 6 Mar 2007, Davide Libenzi wrote:
I assume that the *only* reason for having multiple dentries is really
just the output in /proc/<pid>/fd/, right? Or is there any other reason to
have separate dentries for these pseudo-files?
It's a bit sad to waste that much memory (and time) on something like
that. I bet that the dentry setup is a noticeable part of the whole
sigfd()/timerfd() setup. It's likely also a big part of any memory
footprint if you have lots of them.
So how about just doing:
- do a single dentry
- make a "struct file_operations" member function that prints out the
name of the thing in /proc/<pid>/fd/, and which *defaults* to just
doing the d_path() on the dentry, but special filesystems like this
could do something else (like print out a fake inode number from the
"file->f_private_data" information)
There seems to really be no downsides to that approach. No existing
filesystem will even notice (they'll all have NULL in the new f_op
member), and it would allow pipes etc to be sped up and use less memory.
Linus
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