Re: Fusion-MPT much faster as module

[Andrew Morton <akpm@osdl.org>]

"Chen, Kenneth W" <kenneth.w.chen@intel.com> wrote:
>
> On Mon, 21 Mar 2005, Andrew Morton wrote:
> > Holger, this problem remains unresolved, does it not?  Have you done any
> > more experimentation?
> >
> > I must say that something funny seems to be happening here.  I have two
> > MPT-based Dell machines, neither of which is using a modular driver:
> >
> > akpm:/usr/src/25> 0 hdparm -t /dev/sda
> >
> > /dev/sda:
> > Timing buffered disk reads:  64 MB in  5.00 seconds = 12.80 MB/sec
> 
> 
> Holger Kiehl wrote on Tuesday, March 22, 2005 12:31 AM
> > Got the same result when compiled in, always between 12 and 13 MB/s. As
> > module it is approx. 75 MB/s.
> 
> 
> Half guess, half with data to prove: it must be the variable driver_setup
> initialization.  If compiled as built-in, driver_setup is initialized to
> zero for all of its member variables, which isn't the fastest setting. If
> compiled as module, it gets first class treatment with shinny performance
> setting.  Goofing around, this patch appears to be giving higher throughput.

ooh, you actually looked at the code ;)

> Before:
> /dev/sdc:
>  Timing buffered disk reads:   92 MB in  3.03 seconds =  30.32 MB/sec
> 
> After:
> /dev/sdc:
>  Timing buffered disk reads:  174 MB in  3.02 seconds =  57.61 MB/sec
> 

Yes, that's it.  Eric, you owe me about 10000 hours ;)