[lkml]   [2003]   [Mar]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: High Mem Options
On Wed, 05 Mar 2003 04:26:54 PST, William Lee Irwin III wrote:
> On Wed, Mar 05, 2003 at 06:28:36AM -0500, Reed, Timothy A wrote:
> > Yet another quick there any down side to using the
> > 64GB option over the 4GB option if the machine only has 2GB of RAM onboard??
> > I would think this would be a performance issue? Does the kernel only use
> > the translation table if it has to access any memory location over 4GB?
> Yes, the additional level of pagetables slows things down quite a bit.

Bill, do you hvae measures for this? I seem to remember PTX's impact
of PAE36 as being about 3-5% depending on workload. Janet did one test
sometime back with DB2 that showed a net of no difference on TPC-H (PAE
slows things down, less memory pressure speeds things up) but Badari
just repeated with 2.5.62 or 2.5.63 and saw a larger degradation.

I'm wondering if some hardware is not getting correctly configured at
boot with with respect to MTRR's, perhaps... I really wouldn't expect
a 10% impact from PAE and I don't have any consistent Linux measurements
to validate or invalidate that much impact.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:33    [W:0.057 / U:0.064 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site