Re: [PATCH] add a clear_pages function to clear pages of higher order

[Denis Vlasenko]

On Friday 18 March 2005 21:28, Andi Kleen wrote:
> On Fri, Mar 18, 2005 at 07:00:06AM -0800, Christoph Lameter wrote:
> > On Fri, 18 Mar 2005, Denis Vlasenko wrote:
> > 
> > > NT stores are not about 5% increase. 200%-300%. Provided you are ok with
> > > the fact that zeroed page ends up evicted from cache. Luckily, this is exactly
> > > what you want with prezeroing.
> > 
> > These are pretty significant results. Maybe its best to use non-temporal
> 
> The differences are actually less. I do not know what Denis benchmarked,
> but in my tests the difference was never more than ~10%.  He got a zero
> too much? 

No. See attached.

# gcc -O2 0main.c
# ./a.out
Page clear/copy benchmark program.
buffer size: 1 Mb
Each test tried 64 times, max and min CPU cycles per page are reported.
Please disregard max values. They are due to system interference only.
clear_page() tests:
               normal_clear_page - took 44214 max,12615 min cycles per page
               normal_clear_page - took 18969 max,12649 min cycles per page
             repstosl_clear_page - took 19897 max,12655 min cycles per page
                 movq_clear_page - took 39391 max,10782 min cycles per page
               movntq_clear_page - took 21612 max, 4779 min cycles per page

copy_page() tests:
....

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