From: "Jose R. Santos" <jrsantos@austin.ibm.com>
Subject: BKL removal from find_exported_dentry()
Date: Tue, 9 Mar 2004 07:54:51 -0600
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <20040309135451.GC30766@rx8.ibm.com>
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To: nfs@lists.sourceforge.net
Errors-To: nfs-admin@lists.sourceforge.net

Hi all

I was running SpecSFS on a 8-way machine when I encounter a situation were 
find_exported_dentry() was showing up to 75% in my profiles.  After some 
digging, the problem was trigger when the system was under memory pressure 
which cause a dramatic shrinkage in dcache entries.  This shrinkage cause the 
code path thats held under the BKL to be hit under a few filesystems (XFS, JFS 
and EXT3).

At first glance, the BKL seem over kill since I don't see it protecting 
anything that not already protected by other locks inside the code path.  I 
went ahead and removed the kernel lock from find_exported_dentry() and after 
several hours of testing different loads and different filesystems I have yet 
to see any kernel badness or
NFS call failures.

Is there anything in particular the BKL is trying to protect here or is it 
safe to remove?

-JRS


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