Subject: Re: UBC info
To: Chuck Silvers <>
From: Bill Studenmund <>
List: tech-kern
Date: 06/16/1999 11:46:58
On Wed, 16 Jun 1999, Chuck Silvers wrote:

> I'm guessing the performance difference would be noticable, yea.

Is this a performance hit in all cases, or only in EIO cases?

> now that I think about this a moment, it's actually not that hard to solve.
> we can add a new "p_faulterror" field to struct proc, which is cleared
> at the top of the page-fault handler and set to an errno when a fault is
> not going to be resolved.  then the users of pcb_onfault can check
> p_faulterror to get a real errno, falling back on EFAULT if p_faulterror
> is 0.  I haven't thought thru all the details, but I think this would work.

Given that pcb_onfault would know when to return the error code - the fact
that p_faulterror == 0 doesn't indicate an error-free situation - why not
just initialize it to EFAULT, and let other faulters change the error as

AFAICT in the general case, all we've added is a store (init to EFAULT)
and the extra int in the struct (and any copies of this int).

Take care,