From: Nico Pache <npache@redhat.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
muchun.song@linux.dev, akpm@linux-foundation.org,
willy@infradead.org, gerald.schaefer@linux.ibm.com,
sidhartha.kumar@oracle.com
Subject: Re: [RFC V2] mm: add the zero case to page[1].compound_nr in set_compound_order
Date: Tue, 13 Dec 2022 16:53:30 -0700 [thread overview]
Message-ID: <CAA1CXcB653kDtF90oWUgVA3TDUrJHac-WPe1HdsQtRwtN5B3gA@mail.gmail.com> (raw)
In-Reply-To: <Y5kPKpNp5qCnZEWy@monkey>
Hi Mike,
Thanks for the pointer! Would the branchless conditional be an
improvement over the current approach? I'm not sure how hot this path
is, but it may be worth the optimization.
-- Nico
On Tue, Dec 13, 2022 at 4:48 PM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 12/13/22 16:45, Nico Pache wrote:
> > Since commit 1378a5ee451a ("mm: store compound_nr as well as
> > compound_order") the page[1].compound_nr must be explicitly set to 0 if
> > calling set_compound_order(page, 0).
> >
> > This can lead to bugs if the caller of set_compound_order(page, 0) forgets
> > to explicitly set compound_nr=0. An example of this is commit ba9c1201beaa
> > ("mm/hugetlb: clear compound_nr before freeing gigantic pages")
>
> There has been some recent work in this area. The latest patch being,
> https://lore.kernel.org/linux-mm/20221213212053.106058-1-sidhartha.kumar@oracle.com/
>
> --
> Mike Kravetz
>
next prev parent reply other threads:[~2022-12-13 23:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-13 23:45 Nico Pache
2022-12-13 23:47 ` Mike Kravetz
2022-12-13 23:53 ` Nico Pache [this message]
2022-12-14 0:27 ` Nico Pache
2022-12-14 1:02 ` Mike Kravetz
2022-12-14 6:38 ` Sidhartha Kumar
2022-12-15 1:05 ` Nico Pache
2022-12-14 17:04 ` Matthew Wilcox
2022-12-15 2:48 ` Nico Pache
2022-12-15 21:38 ` Nico Pache
2022-12-15 21:47 ` Matthew Wilcox
2022-12-15 22:02 ` Nico Pache
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