RE: 2.6.10-mm3 scaling problem with inotify

[Zou, Nanhai]

> -----Original Message-----
> From: Zou, Nanhai
> Sent: Friday, January 14, 2005 10:28 AM
> To: 'John McCutchan'
> Subject: RE: 2.6.10-mm3 scaling problem with inotify
> 
> > From: linux-kernel-owner@xxxxxxxxxxxxxxx
> > [mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of John
McCutchan
> > Sent: Friday, January 14, 2005 9:31 AM
> > To: Robert Love
> > Cc: John Hawkes; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: 2.6.10-mm3 scaling problem with inotify
> >
> > On Thu, 2005-01-13 at 19:49 -0500, Robert Love wrote:
> > > On Thu, 2005-01-13 at 15:56 -0800, John Hawkes wrote:
> > > [snip]
> > >
> > > I am open to other ideas, too, but I don't see any nice shortcuts
like
> > > what we can do in inotify_inode_queue_event().
> > >
> > > (Other) John?  Any ideas?
> >
> > No, you covered things well. This code was really just a straight
copy
> > of the dnotify code. Rob cleaned it up at some point, giving us what
we
> > have today. The only fix I can think of is the one suggested by Rob
--
> > copying the dnotify code again.

 
 There is still a little difference between your implement in
 inotify_dentry_parent_queue_event from dnotify_parent
 
 In dnotify_parent, if parent is not watching the event, the code will
not fall
 through dget and dput path.
 
 While in inotify_dentry_parent_queue_event kernel will go dget and dput
even
 if (inode->inotify_data == NULL).
 
 While dget and dput will introduce a lot of atomic operations..
 And the most important, dput will grab global dcache_lock...,
 I think that is the reason why John Hawkes saw great performance drop.
 
 Simply follow dnotify_parent, only call dget and dput when
inode->inotify_data != NULL will solve this problem I think.

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