Re: [PATCH 10/25] Unionfs: add un/likely conditionals on copyup ops

[Kok, Auke]

Erez Zadok wrote:
 Signed-off-by: Erez Zadok [EMAIL PROTECTED]
 ---
  fs/unionfs/copyup.c |  102 +-
  1 files changed, 51 insertions(+), 51 deletions(-)
 
 diff --git a/fs/unionfs/copyup.c b/fs/unionfs/copyup.c
 index 23ac4c8..e3c5f15 100644
 --- a/fs/unionfs/copyup.c
 +++ b/fs/unionfs/copyup.c
 @@ -36,14 +36,14 @@ static int copyup_xattrs(struct dentry *old_lower_dentry,
  
   /* query the actual size of the xattr list */
   list_size = vfs_listxattr(old_lower_dentry, NULL, 0);
 - if (list_size = 0) {
 + if (unlikely(list_size = 0)) {


I've been told several times that adding these is almost always bogus - either 
it
messes up the CPU branch prediction or the compiler/CPU just does a lot better 
at
finding the right way without these hints.

Adding them as a blanket seems rather strange. Have you got any numbers that 
this
really improves performance?

Auke
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Re: Versioning file system

[Kok, Auke]

Jack Stone wrote:

I hope I got the CC list right. Apologies to anyone in didn't include
and anyone I shouldn't have included.

The basic idea is to include an idea from VMS that seems to be quite
useful: version numbers for files.


snip

have you looked into ext3cow? it allows you to take snapshots of the entire ext3 
fs at a single point, and rollback / extract snapshots at any time later. This 
may be sufficient for you and the implementation seems to be rather stable already.


Cheers,

Auke


http://www.ext3cow.com/
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