Re: [resend][PATCH] mm: Restore zone->all_unreclaimable to independence word

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Jan 14, 2010 at 03:14:10PM +0800, KOSAKI Motohiro wrote:
> > On Thu, 14 Jan 2010, KOSAKI Motohiro wrote:
> > 
> > > commit e815af95 (change all_unreclaimable zone member to flags) chage
> > > all_unreclaimable member to bit flag. but It have undesireble side
> > > effect.
> > > free_one_page() is one of most hot path in linux kernel and increasing
> > > atomic ops in it can reduce kernel performance a bit.
> > > 
> > > Thus, this patch revert such commit partially. at least
> > > all_unreclaimable shouldn't share memory word with other zone flags.
> > > 
> > 
> > I still think you need to quantify this; saying you don't have a large 
> > enough of a machine that will benefit from it isn't really a rationale for 
> > the lack of any data supporting your claim.  We should be basing VM 
> > changes on data, not on speculation that there's a measurable impact 
> > here.
> > 
> > Perhaps you could ask a colleague or another hacker to run a benchmark for 
> > you so that the changelog is complete?
> 
> ok, fair. although I dislike current unnecessary atomic-ops.
> I'll pending this patch until get good data.

I think it's a reasonable expectation to help large boxes.

What we can do now, is to measure if it hurts mainline SMP
boxes. If not, we are set on doing the patch :)

Thanks,
Fengguang