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Message-ID: <4402D039.1050307@yahoo.com.au>
Date: Mon, 27 Feb 2006 21:11:05 +1100
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: john@johnmccutchan.com
CC: Andrew Morton <akpm@osdl.org>, holt@sgi.com, linux-kernel@vger.kernel.org,
       rml@novell.com, arnd@arndb.de, hch@lst.de,
       Dipankar Sarma <dipankar@in.ibm.com>
Subject: Re: udevd is killing file write performance.
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John McCutchan wrote:
> On Fri, 2006-24-02 at 18:07 +1100, Nick Piggin wrote:

>>I saw this problem when testing my lockless pagecache a while back.
>>
>>Attached is a first implementation of what was my idea then of how
>>to solve it... note it is pretty rough and I never got around to doing
>>much testing of it.
>>
>>Basically: moves work out of inotify event time and to inotify attach
>>/detach time while staying out of the core VFS.
> 
> 
> 
> This looks really good. There might be some corner cases but it looks
> like it will solve this problem nicely.
> 

Thanks. You should see I sent a new version which fixes several bugs
and cleans up the code a bit.

There might be some areas of potential problems:
- creating and deleting watches on directories with many entries will
   take a long time. Is anyone likely to be creating and destroying
   these things at a very high frequency? Probably nobody cares except
   it might twist some real-time knickers.

- concurrent operations in the same watched directory will incur the
   same scalability penalty. I think this is basically a non-issue since
   the sheer number of events coming out will likely be a bigger problem.
   Doctor, it hurts when I do this.

-- 
SUSE Labs, Novell Inc.
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