F16 unusable while writing to pendrive [SOLVED]

[Patrick O'Callaghan]

On Sat, 2011-12-17 at 21:17 -0430, Patrick O'Callaghan wrote:
> On Sun, 2011-12-18 at 01:37 +0000, Marko Vojinovic wrote:
> > On Saturday 17 December 2011 19:41:38 Patrick O'Callaghan wrote:
> > > This looks like a regression. Under F15 when I wrote large files to a
> > > pendrive, the system would become a little sluggish. Now it essentially
> > > freezes until the write terminates. What I mean is that the UI is almost
> > > completely unresponsive; even clicking between two terminal windows is
> > > so slow that you can see the window contents refresh, followed several
> > > seconds later by the frame.
> > > 
> > > Fully updated F16 with KDE, Intel Core 2 Dual, 4GB RAM, Intel onboard
> > > graphics. The pendrive is an 8GB Patriot Xporter (a year or two old)
> > > under USB-2 with no intervening hub.
> > 
> > Oh yes, this is one of my favourities... :-D
> > 
> > There's a very good article at LWN discussing precisely this issue:
> > 
> >    http://lwn.net/Articles/467328/
> > 
> > You wouldn't believe how complicated these things can get... ;-) One would 
> > naively think "yes, the USB drive is slow, but that shouldn't stop the rest of 
> > the system from running smoothly". However, when you put into the mix the 
> > hugemem page allocation, memory fragmentation, contradictory points of view on 
> > how the kernel should be optimized, etc., it seems that it is quite natural 
> > that your typical fast 3GHz system with 4GB of RAM grinds to a complete halt 
> > during a simple write-to-USB-drive operation... :-D
> 
> That might be it I guess, but I'm not totally convinced. I updated
> F15->F16 only 5 days ago, and previous to the switchover had no problems
> of this sort, using the latest kernel for F15. It's hard to believe the
> kernel switch from F15 to F16 can have made such a huge difference. For
> the record, I went from:
> 
>         kernel-2.6.41.1-1.fc15.x86_64
> 
> to:
> 
>         kernel-3.1.5-1.fc16.x86_64
> 
> But as we know, the version bump from 2 to 3 is meaningless in itself.

This was really bothering me (I make frequent use of pendrives) so took
another look at the above article, then
at /usr/share/doc/kernel-doc-3.1.9/Documentation/vm/transhuge.txt, where
it explains how to turn off the Transparent Huge Pages feature. I added
transparent_hugepage=never to my boot params, rebooted, and the problem
appears to have been fixed.

Note: YMMV. This works for me with my workload (no long jobs or
intensive compute load). Others may find it impacts their performance,
but it shouldn't break anything.

poc