From: "Bill Rugolsky Jr." <brugolsky@telemetry-investments.com>
Subject: Re: knfsd brought to its knees, by a simple rsync or cp operation
Date: Tue, 1 Mar 2005 10:04:46 -0500
Message-ID: <20050301150446.GD4848@ti64.telemetry-investments.com>
References: <20050226082854.2a496ec3@be.back.l8r.net> <20050228100633.GA4822@suse.de> <20050228102307.3788a184@be.back.l8r.net> <20050228154455.GS4822@suse.de> <20050228112018.34fdeb2b@be.back.l8r.net> <20050301095548.GJ14402@suse.de> <20050301065703.7e52cf4e@be.back.l8r.net>
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Cc: nfs@lists.sourceforge.net
To: Brad Barnett <lists@L8R.net>
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On Tue, Mar 01, 2005 at 06:57:03AM -0500, Brad Barnett wrote:
> However, this is what is really erking me.  This isn't a heavy I/O job. 
> This is just _one_ cp.  Nothing else is happening on the entire server!  I
> just did, in the above test:
> 
> client: ls -R /home
> 
> The client is fine, for very long periods of time...
> 
> Then, while the above command is still happening:
> 
> server: cp -a /raid/home /raid/hometest

You say that it isn't a heavy I/O job, but a recursive copy is a very
seek-intensive one, particularly when copying a large tree to the same
device, which will interleave reads and writes.  What filesystem are you
using?  With an internal journal, journal writes will cause additional seeking.
 
> Within 10 seconds, the output of ls -R /home slows.  Within 20 seconds, it
> _stop_.  It then sits there for seconds, and spews out a page in small
> jumps.  Again, a ls /raid/home on the _server_ barely slows, and is
> constant.

Do you mean ls -R /raid/home here?  Is it definitely the case that
ls -R /raid/home on the server is quick, but on the client it is slow?

How about ls -lR /raid/home on the server?  It could be that knfsd is
returning file attribute information, hence reading the whole inode
for each file, and not just for the directories.  getdents64() returns
d_type=DT_DIR for directory entries, which allows ls -R to optimize the
traversal so as to only call fstat64() on directories, not regular files.
So on the server, ls -R would only fstat64() the entries, while
on the client ls -R can cause knfsd to do the equivalent of ls -lR.

Also, which I/O scheduler are you using?

Regards,

	Bill Rugolsky


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