linux-kernel - Re: [PATCH 1/1] mm/mlock: implement folio_mlock_step() using folio_pte

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Date: Mon, 3 Jun 2024 12:13:25 +0800
From: Lance Yang <ioworker0@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: akpm@...ux-foundation.org, ryan.roberts@....com, david@...hat.com, 
	21cnbao@...il.com, baolin.wang@...ux.alibaba.com, ziy@...dia.com, 
	fengwei.yin@...el.com, ying.huang@...el.com, libang.li@...group.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] mm/mlock: implement folio_mlock_step() using folio_pte_batch()

Hi Matthew,

Thanks for taking time to review!

On Mon, Jun 3, 2024 at 11:36 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Mon, Jun 03, 2024 at 11:31:17AM +0800, Lance Yang wrote:
> >  {
> > -     unsigned int count, i, nr = folio_nr_pages(folio);
> > -     unsigned long pfn = folio_pfn(folio);
> > -     pte_t ptent = ptep_get(pte);
>
> Please don't move type declarations later in the function.  Just because
> you can doesn't mean you should.

Thanks for pointing this out, I'll adjust as you suggested.

>
> > -     if (!folio_test_large(folio))
> > +     if (likely(!folio_test_large(folio)))
> >               return 1;
>
> How likely is this now?  How likely will it be in two years time?
> Does this actually make any difference in either code generation or
> performance?

IMO, this hint could impact code generation and performance :)
But it seems that 'likely' is not necessary here. I'll remove it.

Thanks again for your time!
Lance

>