linux-kernel - Re: [RFC][Resend] Make NFS-Client readahead tunable

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Date:	Wed, 17 Sep 2008 09:15:45 -0700 (PDT)
From:	Martin Knoblauch <knobi@...bisoft.de>
To:	Michael Trimarchi <trimarchimichael@...oo.it>,
	linux-nfs list <linux-nfs@...r.kernel.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC][Resend] Make NFS-Client readahead tunable

----- Original Message ----

> From: Michael Trimarchi <trimarchimichael@...oo.it>
> To: Martin Knoblauch <knobi@...bisoft.de>; linux-nfs list <linux-nfs@...r.kernel.org>
> Cc: linux-kernel@...r.kernel.org
> Sent: Wednesday, September 17, 2008 3:42:30 PM
> Subject: Re: [RFC][Resend] Make NFS-Client readahead tunable
> 
> Hi,
> 
> ...
> 
> > Signed-off-by: Martin Knoblauch 
> > 
> > diff -urp linux-2.6.27-rc6-git4/fs/nfs/client.c 
> > linux-2.6.27-rc6-git4-nfs_ra/fs/nfs/client.c
> > --- linux-2.6.27-rc6-git4/fs/nfs/client.c       2008-09-17 11:35:21.000000000 
> > +0200
> > +++ linux-2.6.27-rc6-git4-nfs_ra/fs/nfs/client.c        2008-09-17 
> > 11:55:18.000000000 +0200
> > @@ -722,6 +722,11 @@ error:
> > }
> > 
> > /*
> > + * NFS Client Read-Ahead factor
> > +*/
> > +unsigned int nfs_ra_factor;
> > +
> > +/*
> >   * Load up the server record from information gained in an fsinfo record
> >   */
> > static void nfs_server_set_fsinfo(struct nfs_server *server, struct nfs_fsinfo 
> 
> > *fsinfo)
> > @@ -746,7 +751,11 @@ static void nfs_server_set_fsinfo(struct
> >                 server->rsize = NFS_MAX_FILE_IO_SIZE;
> >         server->rpages = (server->rsize + PAGE_CACHE_SIZE - 1) >> 
> > PAGE_CACHE_SHIFT;
> > 
> > -       server->backing_dev_info.ra_pages = server->rpages * 
> NFS_MAX_READAHEAD;
> > +       dprintk("nfs_server_set_fsinfo: rsize, wsize, rpages, \
> > +               nfs_ra_factor, ra_pages: %d %d %d %d %d\n",
> > +               server->rsize,server->wsize,server->rpages,
> > +               nfs_ra_factor,server->rpages * nfs_ra_factor);
> > +       server->backing_dev_info.ra_pages = server->rpages * nfs_ra_factor;
> > 
> >         if (server->wsize > max_rpc_payload)
> >                 server->wsize = max_rpc_payload;
> > diff -urp linux-2.6.27-rc6-git4/fs/nfs/inode.c 
> > linux-2.6.27-rc6-git4-nfs_ra/fs/nfs/inode.c
> > --- linux-2.6.27-rc6-git4/fs/nfs/inode.c        2008-09-17 11:35:21.000000000 
> > +0200
> > +++ linux-2.6.27-rc6-git4-nfs_ra/fs/nfs/inode.c 2008-09-17 11:45:09.000000000 
> > +0200
> > @@ -53,6 +53,8 @@
> > 
> > /* Default is to see 64-bit inode numbers */
> > static int enable_ino64 = NFS_64_BIT_INODE_NUMBERS_ENABLED;
> > +static unsigned int ra_factor __read_mostly = NFS_MAX_READAHEAD;
> > +
> > 
> > static void nfs_invalidate_inode(struct inode *);
> > static int nfs_update_inode(struct inode *, struct nfs_fattr *);
> > @@ -1347,6 +1349,12 @@ static int __init init_nfs_fs(void)
> > #endif
> >         if ((err = register_nfs_fs()) != 0)
> >                 goto out;
> > +
> > +       if (ra_factor < 1 || ra_factor > NFS_MAX_READAHEAD)
> > +               nfs_ra_factor = NFS_MAX_READAHEAD;
> > +       else
> > +               nfs_ra_factor = ra_factor;
> > +
> 
> So, I think that this is not necessary because it is done ( ... I hope) by the 
> proc_dointvec_minmax handler. It is correct?
> 

That is of course true if the tunable is changed via the /proc interface. The code above handles the module parameter, which is not governed by the minmax handler.

Cheers
Martin

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