Subject: Re: Please Revert newlock2
To: None <tech-kern@netbsd.org>
From: Bucky Katz <bucky@picovex.com>
List: tech-kern
Date: 02/20/2007 15:40:45
Jason Thorpe <thorpej@shagadelic.org> writes:

> On Feb 20, 2007, at 2:54 PM, Bucky Katz wrote:
>
>> The only ways you can address the performance problems with context
>> switching on ARM are to either a) reduce the number of context
>> switches you do on ARM or b) move to ARM11.
>
> I worked on low-level ARM stuff as part of my Day Job for a few
> years, and I'm not quite seeing where this comment is coming from
> when thinking in the context of SWITCHING TO ANOTHER LWP WITHIN THE
> SAME PROCESS (meaning that the address space is not changing, thus
> meaning that there is no need to flush the cache or or the TLB).

That's because you're conflating two separate problems.  the context
switch issues on ARM are with switching between processes.  It's not
context switching that drives the desire for M:N on ARM, as I mentioned
elsewhere.