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

From: David Rientjes
Date: Thu Jan 14 2010 - 01:33:20 EST

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

Perhaps you could ask a colleague or another hacker to run a benchmark for
you so that the changelog is complete?
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