lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date:	Fri, 28 Dec 2007 10:33:21 +0800
From:	Fengguang Wu <>
To:	saeed bishara <>
Cc:	Jeff Garzik <>,,
	NFS list <>
Subject: Re: read-ahead in NFS server

On Thu, Dec 27, 2007 at 05:00:12PM +0200, saeed bishara wrote:
> > >> Are you using TCP?  Are you using NFSv4, or an older version?
> > > I'm using NFSv3/UDP.
> >
> > IMO, you definitely want TCP and NFSv4.  Much better network behavior,
> > with some of the silly UDP limits (plus greatly improved caching
> > behavior, due to v4 delegations).
> the clients of my system going to be embedded system with low
> performance cpus and I need UDP as it needs less cpu power.

You can try the attached adaptive readahead patch.
Apply it on your server and compile kernel with CONFIG_ADAPTIVE_READAHEAD.
Use large 1MB readahead on server and small readahead on clients.

> > > when I run local dd with bs=4K, I can see that the average IO size is
> > > more than 300KB.
> >
> > Read-ahead is easier in NFSv4, because the client probably has the file
> > delegated locally, and has far less need to constantly revalidate file
> > mapping(s).
> I'll check that.
> but what about the server side? why the issued IO's are only as twice
> as the size of the NFS requests?

The readahead code is helpless in NFSv3 :-(
Use NFS over TCP and rsize=readahead=1MB on client side could help.
But if you prefer UDP, the above patch may help you :-)


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists