Re: [PATCH] Faster ext2_clear_inode()

2007-07-19 Thread Andrew Morton 
On Mon, 9 Jul 2007 22:00:03 +0200
Jörn Engel [EMAIL PROTECTED] wrote:

 On Mon, 9 July 2007 22:01:48 +0400, Alexey Dobriyan wrote:
  
  Yes. Note that ext2_clear_inode() is referenced from ext2_sops, so even
  empty, it leaves traces in resulting kernel.
 
 Is that your opinion or have you actually measured a difference?
 I strongly suspect that compilers are smart enough to optimize away a
 call to an empty static function.
 

It saves a big 16 bytes of text here.
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Re: [PATCH] Faster ext2_clear_inode()

2007-07-09 Thread Jörn Engel 
On Mon, 9 July 2007 08:11:22 +0400, Alexey Dobriyan wrote:
 
 If CONFIG_EXT2_FS_POSIX_ACL is not configured, ext2_clear_inode() will be 
 empty
 function. However, there still will be call and immediate return which can be
 avoided.
 [...]
 +#ifdef CONFIG_EXT2_FS_POSIX_ACL
  static void ext2_clear_inode(struct inode *inode)
  {
 -#ifdef CONFIG_EXT2_FS_POSIX_ACL
   struct ext2_inode_info *ei = EXT2_I(inode);
  
   if (ei-i_acl  ei-i_acl != EXT2_ACL_NOT_CACHED) {
 @@ -197,8 +197,10 @@ static void ext2_clear_inode(struct inode *inode)
   posix_acl_release(ei-i_default_acl);
   ei-i_default_acl = EXT2_ACL_NOT_CACHED;
   }
 -#endif
  }
 +#else
 +#define ext2_clear_inode NULL
 +#endif

Are you sure your patch makes a difference?  Does the resulting binary
change at all?

Jörn

-- 
Fancy algorithms are slow when n is small, and n is usually small.
Fancy algorithms have big constants. Until you know that n is
frequently going to be big, don't get fancy.
-- Rob Pike
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Re: [PATCH] Faster ext2_clear_inode()

2007-07-09 Thread Alexey Dobriyan 
On Mon, Jul 09, 2007 at 10:34:32AM +0200, Jörn Engel wrote:
 On Mon, 9 July 2007 08:11:22 +0400, Alexey Dobriyan wrote:
  
  If CONFIG_EXT2_FS_POSIX_ACL is not configured, ext2_clear_inode() will be 
  empty
  function. However, there still will be call and immediate return which can 
  be
  avoided.
  [...]
  +#ifdef CONFIG_EXT2_FS_POSIX_ACL
   static void ext2_clear_inode(struct inode *inode)
   {
  -#ifdef CONFIG_EXT2_FS_POSIX_ACL
  struct ext2_inode_info *ei = EXT2_I(inode);
   
  if (ei-i_acl  ei-i_acl != EXT2_ACL_NOT_CACHED) {
  @@ -197,8 +197,10 @@ static void ext2_clear_inode(struct inode *inode)
  posix_acl_release(ei-i_default_acl);
  ei-i_default_acl = EXT2_ACL_NOT_CACHED;
  }
  -#endif
   }
  +#else
  +#define ext2_clear_inode NULL
  +#endif
 
 Are you sure your patch makes a difference?  Does the resulting binary
 change at all?

Yes. Note that ext2_clear_inode() is referenced from ext2_sops, so even
empty, it leaves traces in resulting kernel.

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Re: [PATCH] Faster ext2_clear_inode()

2007-07-09 Thread Jörn Engel 
On Mon, 9 July 2007 22:01:48 +0400, Alexey Dobriyan wrote:
 
 Yes. Note that ext2_clear_inode() is referenced from ext2_sops, so even
 empty, it leaves traces in resulting kernel.

Is that your opinion or have you actually measured a difference?
I strongly suspect that compilers are smart enough to optimize away a
call to an empty static function.

Jörn

-- 
Fancy algorithms are slow when n is small, and n is usually small.
Fancy algorithms have big constants. Until you know that n is
frequently going to be big, don't get fancy.
-- Rob Pike
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Re: [PATCH] Faster ext2_clear_inode()

2007-07-09 Thread Dave Kleikamp 
On Mon, 2007-07-09 at 22:00 +0200, Jörn Engel wrote:
 On Mon, 9 July 2007 22:01:48 +0400, Alexey Dobriyan wrote:
  
  Yes. Note that ext2_clear_inode() is referenced from ext2_sops, so even
  empty, it leaves traces in resulting kernel.
 
 Is that your opinion or have you actually measured a difference?
 I strongly suspect that compilers are smart enough to optimize away a
 call to an empty static function.

It's not a direct call to a static function.  It is called as a
super_ops method.  I don't think the overhead is very significant, but
it doesn't look like it could do any harm.

-- 
David Kleikamp
IBM Linux Technology Center

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Re: [PATCH] Faster ext2_clear_inode()

2007-07-09 Thread Jörn Engel 
On Mon, 9 July 2007 17:02:20 -0500, Dave Kleikamp wrote:
 
 It's not a direct call to a static function.  It is called as a
 super_ops method.  I don't think the overhead is very significant, but
 it doesn't look like it could do any harm.

Ah, I missed that fact.  Yep, looks fine to me.

Jörn

-- 
Joern's library part 7:
http://www.usenix.org/publications/library/proceedings/neworl/full_papers/mckusick.a
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[PATCH] Faster ext2_clear_inode()

2007-07-08 Thread Alexey Dobriyan 
If CONFIG_EXT2_FS_POSIX_ACL is not configured, ext2_clear_inode() will be empty
function. However, there still will be call and immediate return which can be
avoided.

Signed-off-by: Alexey Dobriyan [EMAIL PROTECTED]
---

 fs/ext2/super.c |6 --
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -184,9 +184,9 @@ static void destroy_inodecache(void)
kmem_cache_destroy(ext2_inode_cachep);
 }
 
+#ifdef CONFIG_EXT2_FS_POSIX_ACL
 static void ext2_clear_inode(struct inode *inode)
 {
-#ifdef CONFIG_EXT2_FS_POSIX_ACL
struct ext2_inode_info *ei = EXT2_I(inode);
 
if (ei-i_acl  ei-i_acl != EXT2_ACL_NOT_CACHED) {
@@ -197,8 +197,10 @@ static void ext2_clear_inode(struct inode *inode)
posix_acl_release(ei-i_default_acl);
ei-i_default_acl = EXT2_ACL_NOT_CACHED;
}
-#endif
 }
+#else
+#define ext2_clear_inode NULL
+#endif
 
 static int ext2_show_options(struct seq_file *seq, struct vfsmount *vfs)
 {

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