[ltp] Thinkpad T43 cached read Speed(hdparm -T) mystery

[Henrique de Moraes Holschuh]

On Wed, 25 Jun 2008, Henrique de Moraes Holschuh wrote:
> On Wed, 25 Jun 2008, jqian@physics.harvard.edu wrote:
> > > If the regression in hdparm -T speed is indeed related to ZEROPAGE, that
> > > means hdparm -T is a completely meaningless test.
> > I'm sorry to be a bit dense here, but if 2.6.25.9 fix a "performance 
> > regression", then what hdparm -T detects is a real regression, not a 
> > meaningless test, right?
> 
> Sort of :-)  It is a regression on pages filled with zeros, you usually
> don't have to *read* a lot from such pages, hmm?
> 
> The big part of the regression was in memory wastage, not speed to access
> the data... but it might have made read access to them slower too (due to
> cache).
> 
> > > Your real workload is the only gauge for performance that matters.
> > It's hard for me to judge performances when I had distro change, is 
> > there some benchmark that more sensibly reflect the bus speed of my 
> > computer?
> 
> bonie++ for filesystems, and a few other benchmarking stuff for certain
> styles of workloads (such as hackbench, etc).  But really, if you can't feel
> or measure that the computer is doing what waitn it to do to be any slower,
> what is the point?

I sincerely don't know what happened to that paragraph :)  Here's a
corrected version...

But really, if you cannot feel or measure that whatever you need the
computer do to is any slower, what is the point of bothering with
benchmarks?

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh