Re: O->A loan

[Chuck Silvers <chuq%chuq.com@localhost>]

On Sat, Feb 18, 2012 at 08:22:35PM +0000, Mindaugas Rasiukevicius wrote:
> yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi) wrote:
> > hi,
> > 
> > i'd like to to either fix or remove O->A page loaning.
> > 
> > the biggest problem is the lack of users.  thus no way to test.
> > any ideas?
> 
> After looking at O->A loaning code in yamt-pagecache branch, looking at
> the benchmark results by Jaime (some data was sent privately, I think)
> and contemplating about this mechanism - I tend to think that O->A loaning
> should be removed.  It is a significant code complexity in UVM with some
> special casing and benchmarks indicate that the benefit is somewhat small.
> 
> Does not seem to be worth, does it?

making this conclusion on the basis of a single benchmark seems premature.
the use of O->A loaning in that branch is for optimizing reads,
was that benchmark even doing many reads?

give me a few days and I'll see if I can come up with some other benchmarks
that tell a different story.

-Chuck