Re: [dm-devel] [Lsf-pc] [LSF/MM TOPIC] a few storage topics

[Wu Fengguang <fengguang wu gmail com>]

On Fri, Jan 27, 2012 at 09:34:49AM +1100, Dave Chinner wrote:
> On Thu, Jan 26, 2012 at 11:25:56AM -0500, Vivek Goyal wrote:
> > On Wed, Jan 25, 2012 at 02:35:52PM +0800, Wu Fengguang wrote:
> > > > It would also be
> > > > possible to trigger on the size of the device so that the 32MB USB stick
> > > > doesn't sit busy for a minute with readahead that is useless.
> > > 
> > > Yeah, I do have a patch for shrinking readahead size based on device size.
> > 
> > Should it be a udev rule to change read_ahead_kb on device based on device
> > size, instead of a kernel patch?
> 
> That's effectively what vendors like SGI have been doing since udev
> was first introduced, though more often the rules are based on device
> type rather than size. e.g. a 64GB device might be a USB flash drive
> now, but a 40GB device might be a really fast SSD....

Fair enough. I'll drop this kernel policy patch 

        block: limit default readahead size for small devices
        https://lkml.org/lkml/2011/12/19/89

Thanks,
Fengguang