linux-kernel - Re: [PATCH v3 1/2] mm: add per-order mTHP split counters

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAK1f24=M0i_Wisf9NHGcyo4wJ90a5QYefm=+rck5XAXMg1QNJQ@mail.gmail.com>
Date: Fri, 5 Jul 2024 18:48:02 +0800
From: Lance Yang <ioworker0@...il.com>
To: David Hildenbrand <david@...hat.com>
Cc: Barry Song <21cnbao@...il.com>, akpm@...ux-foundation.org, dj456119@...il.com, 
	ryan.roberts@....com, shy828301@...il.com, ziy@...dia.com, 
	libang.li@...group.com, baolin.wang@...ux.alibaba.com, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Mingzhe Yang <mingzhe.yang@...com>
Subject: Re: [PATCH v3 1/2] mm: add per-order mTHP split counters

Hi David and Barry,

Thanks a lot for paying attention!

On Fri, Jul 5, 2024 at 6:14 PM David Hildenbrand <david@...hat.com> wrote:
>
> On 05.07.24 12:12, Barry Song wrote:
> > On Fri, Jul 5, 2024 at 9:08 PM David Hildenbrand <david@...hat.com> wrote:
> >>
> >>> @@ -3253,8 +3259,9 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
> >>>                i_mmap_unlock_read(mapping);
> >>>    out:
> >>>        xas_destroy(&xas);
> >>> -     if (is_thp)
> >>> +     if (order >= HPAGE_PMD_ORDER)
> >>
> >> We likely should be using "== HPAGE_PMD_ORDER" here, to be safe for the
> >> future.
> >
> > I feel this might need to be separate since all other places are using
> > folio_test_pmd_mappable() ?
>
> Likely, but as you are moving away from this ... this counter here does
> and will always only care about HPAGE_PMD_ORDER.

I appreciate the different opinions on whether we should use
">= HPAGE_PMD_ORDER" or "==" for this check.

In this context, let's leave it as is and stay consistent with
folio_test_pmd_mappable() by using ">= HPAGE_PMD_ORDER",
what do you think?

Thanks,
Lance

>
> --
> Cheers,
>
> David / dhildenb
>