On 05/30/2011 05:43 PM, Ingo Molnar wrote:
> I agree that using the cpu to clear memory is not a good idea, it
> just causes cache pollution.
Yeah, but even cache-neutral clearing (either driven from the CPU
from the idle thread or by a DMA engine) is not a particularly good
idea: because it uses up a finite resource: memory bandwidth.
I think that on modern machines it's not such an issue, at least
compared to cpu time.
Can we
create 'idle' DMA transactions - once that never get in the way of
real DMA transactions?
Not to my knowledge.
Also, a profile of a typical kernel build shows:
0.69% cc1 [kernel.kallsyms] [k] clear_page_c
0.49% cc1 [kernel.kallsyms] [k] page_fault
So while we could improve it, the question is, can we do this without
accidentally slowing things down by more than 0.69%? And kernel
builds are a pretty clear_page_c() intense workload.
I usually see much higher clear_page_c, but I'm using a pretty old
system for most of my testing.
--
error compiling committee.c: too many arguments to function
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