linux-kernel - Re: [PATCH 1/4] mm: pass set_count and set_reserved to __init_single

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Date:   Fri, 22 Sep 2023 09:48:59 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>,
        Yajun Deng <yajun.deng@...ux.dev>
Cc:     akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        muchun.song@...ux.dev, glider@...gle.com, elver@...gle.com,
        dvyukov@...gle.com, rppt@...nel.org, osalvador@...e.de,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com
Subject: Re: [PATCH 1/4] mm: pass set_count and set_reserved to
 __init_single_page

On 22.09.23 09:47, Matthew Wilcox wrote:
> On Fri, Sep 22, 2023 at 03:09:20PM +0800, Yajun Deng wrote:
>> -		__init_single_page(page, pfn, zone, nid);
>> +		__init_single_page(page, pfn, zone, nid, true, false);
> 
> So Linus has just had a big rant about not doing bool flags to
> functions.  And in particular _multiple_ bool flags to functions.
> 
> ie this should be:
> 
> #define INIT_PAGE_COUNT		(1 << 0)
> #define INIT_PAGE_RESERVED	(1 << 1)
> 
> 		__init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
> 
> or something similar.
> 
> I have no judgement on the merits of this patch so far.  Do you have
> performance numbers for each of these patches?  Some of them seem quite
> unlikely to actually help, at least on a machine which is constrained
> by cacheline fetches.

The last patch contains

before:
node 0 deferred pages initialised in 78ms

after:
node 0 deferred pages initialised in 72ms

Not earth-shattering :D Maybe with much bigger machines relevant?

-- 
Cheers,

David / dhildenb