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Message-ID: <20230922080831.GH3303@kernel.org>
Date: Fri, 22 Sep 2023 11:08:31 +0300
From: Mike Rapoport <rppt@...nel.org>
To: David Hildenbrand <david@...hat.com>
Cc: Matthew Wilcox <willy@...radead.org>,
Yajun Deng <yajun.deng@...ux.dev>, akpm@...ux-foundation.org,
mike.kravetz@...cle.com, muchun.song@...ux.dev, glider@...gle.com,
elver@...gle.com, dvyukov@...gle.com, 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 Fri, Sep 22, 2023 at 09:48:59AM +0200, David Hildenbrand wrote:
> 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?
Patch 3 contains
The following data was tested on an x86 machine with 190GB of RAM.
before:
free_low_memory_core_early() 342ms
after:
free_low_memory_core_early() 286ms
Which is more impressive, but still I'm not convinced that it's worth the
added complexity and potential subtle bugs.
> --
> Cheers,
>
> David / dhildenb
>
--
Sincerely yours,
Mike.
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