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From: Michal Hocko <mhocko@suse.com>
To: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>,
	nao.horiguchi@gmail.com,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: mempolicy: don't have to split pmd for huge zero page
Date: Tue, 8 Jun 2021 19:49:42 +0200	[thread overview]
Message-ID: <YL+ttjqJ9lEMndiA@dhcp22.suse.cz> (raw)
In-Reply-To: <CAHbLzkquqKOL7pH8yBdfpafeHJCUZvccNKjQBucsP7C4k83f7g@mail.gmail.com>

On Tue 08-06-21 10:15:36, Yang Shi wrote:
[...]
> I did some archeology, the findings are:
> 
> The zero page has PageReserved flag set, it was skipped by the
> explicit PageReserved check in mempolicy.c since commit f4598c8b3678
> ("[PATCH] migration: make sure there is no attempt to migrate reserved
> pages."). The zero page was not used anymore by do_anonymous_page()
> since 2.6.24 by commit 557ed1fa2620 ("remove ZERO_PAGE"), then
> reinstated by commit a13ea5b759645 ("mm: reinstate ZERO_PAGE") and
> this commit added zero page check in vm_normal_page(), so mempolicy
> doesn't depend on PageReserved check to skip zero page anymore since
> then.
> 
> So the zero page is skipped by mempolicy.c since 2.6.16.

Thanks a lot! This is really useful. Can you just add it to the
changelog so others do not have to go through the painful archeology.

With that, feel free to add
Acked-by: Michal Hocko <mhocko@suse.com>

Thanls!
-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2021-06-08 17:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-04 20:35 [PATCH] mm: mempolicy: don't have to split pmd for huge zero page Yang Shi
2021-06-04 21:23 ` Zi Yan
2021-06-07  6:21 ` Michal Hocko
2021-06-07 17:00   ` Yang Shi
2021-06-07 17:00     ` Yang Shi
2021-06-07 18:41     ` Yang Shi
2021-06-07 18:41       ` Yang Shi
2021-06-07 18:55     ` Michal Hocko
2021-06-07 22:02       ` Yang Shi
2021-06-07 22:02         ` Yang Shi
2021-06-08  6:41         ` Michal Hocko
2021-06-08 17:15           ` Yang Shi
2021-06-08 17:15             ` Yang Shi
2021-06-08 17:49             ` Michal Hocko [this message]
2021-06-08 19:36               ` Yang Shi
2021-06-08 19:36                 ` Yang Shi

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