Re: Note describing poor dcache utilization under high memory pressure

[Rick Stevens <rstevens@vitalstream.com>]

Daniel Phillips wrote:

> Since the page was copied to the child, the child's page table must be 
> altered, and since it is shared, it must first be instantiated by the child.  
> So after all the dust settles, the parent and child have their own copies of 
> a page table page, which differ only at a single location: the child's page 
> table points at its freshly made CoW copy, and the parent's page table points 
> at the original page.

> 
> The beauty of this is, the page table could just as easily have been shared 
> by a sibling of the child, not the parent at all, in the case that the parent 
> had already instantiated its own copy of the page table page because of an 
> earlier CoW.


Ok.  Still seems like a bit more copying than necessary.  I'd have
to look at it a bit more and do some noodling.

 
> Confused yet?  Welcome to the club ;-)


Does my head exploding qualify for "confused"?  If so, then I'm not
yet "confused".  I'm "concerned", since my ears are bleeding (a
precursor to an explosion) ;-p

----------------------------------------------------------------------
- Rick Stevens, SSE, VitalStream, Inc.      rstevens@vitalstream.com -
- 949-743-2010 (Voice)                    http://www.vitalstream.com -
-                                                                    -
-        "More hay, Trigger?" "No thanks, Roy, I'm stuffed!"         -
----------------------------------------------------------------------