linux-kernel - Re: [PATCH] mm: pass the pfn to set_pageblock

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Message-ID: <Zl3KoETSfL6-RTU1@casper.infradead.org>
Date: Mon, 3 Jun 2024 14:52:32 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Yajun Deng <yajun.deng@...ux.dev>
Cc: akpm@...ux-foundation.org, rppt@...nel.org, hannes@...xchg.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: pass the pfn to set_pageblock_migratetype

On Mon, Jun 03, 2024 at 01:48:50PM +0000, Yajun Deng wrote:
> June 3, 2024 at 9:03 PM, "Matthew Wilcox" <willy@...radead.org> wrote:
> > On Mon, Jun 03, 2024 at 08:41:00PM +0800, Yajun Deng wrote:
> > > It is necessary to calculate the pfn in the set_pageblock_migratetype(),
> > >  but most of the callers already have the pfn.
> > 
> > It's not exactly a hard computation though. Have you done any
> > 
> > measurements that show this patch is an improvement?
> 
> No, just view the code. But some callers are in a for loop.

All the more reason to MEASURE.  There is a cost to marshalling
function arguments which must be weighed against the cost of
recalculating the PFN.  Since you haven't done that, NAK.