Subject: Re: Kernel copyin/out optimizations for ARM...
To: None <>
From: David Laight <>
List: port-arm
Date: 03/13/2002 20:03:31
> The PTE check is actually checking for the 'copy on write' case,
> not the 'page not present' case.  This may have something to do
> with the problems Jason? was having with COW on XSCALE.
> My guess is that the cpu wasn't faulting the write to cache! Just the
> writeback of the cacheline - which would be asynchonous! 

Further thoughts:

1) if this check is needed here, presuambly there are equivalent
   problems for COW for writes from user space?

2) is address space reserved for PTE entries for the entire user
   address space?

3) could one of our pages become COW while we are blocked reading
   in another faulted page?


David Laight: