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Date: Fri, 12 Oct 2018 14:36:45 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
Subject: Re: [PATCH v2 2/2] mm: speed up mremap by 500x on large regions
Message-ID: <20181012113644.meqy5yb3xrxyh6lh@kshutemo-mobl1>
References: <20181012013756.11285-1-joel@joelfernandes.org>
 <20181012013756.11285-2-joel@joelfernandes.org>
 <20181012113056.gxhcbrqyu7k7xnyv@kshutemo-mobl1>
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To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, minchan@kernel.org, pantin@google.com, hughd@google.com, lokeshgidra@google.com, dancol@google.com, mhocko@kernel.org, akpm@linux-foundation.org, Andrey Ryabinin <aryabinin@virtuozzo.com>, Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>, Catalin Marinas <catalin.marinas@arm.com>, Chris Zankel <chris@zankel.net>, Dave Hansen <dave.hansen@linux.intel.com>, "David S. Miller" <davem@davemloft.net>, elfring@users.sourceforge.net, Fenghua Yu <fenghua.yu@intel.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Guan Xuetao <gxt@pku.edu.cn>, Helge Deller <deller@gmx.de>, Ingo Molnar <mingo@redhat.com>, "James E.J. Bottomley" <jejb@parisc-linux.org>, Jeff Dike <jdike@addtoit.com>, Jonas Bonn <jonas@southpole.se>, Julia Lawall <Julia.Lawall@lip6.fr>, kasan-dev@googlegroups.com, kvmarm@lists.cs.columbia.edu, Ley Foon Tan <lftan@altera.com>, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@linux-mips.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org, Max Filippov <jcmvbkbc@gmail.com>, nios2-dev@lists.rocketboards.org, openrisc@lists.librecores.org, Peter Zijlstra <peterz@infradead.org>, Richard Weinberger <richard@nod.at>, Rich Felker <dalias@libc.org>, Sam Creasey <sammy@sammy.net>, sparclinux@vger.kernel.org, Stafford Horne <shorne@gmail.com>, Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>, Thomas Gleixner <tglx@linutronix.de>, Tony Luck <tony.luck@intel.com>, Will Deacon <will.deacon@arm.com>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>, Yoshinori Sato <ysato@users.sourceforge.jp>

On Fri, Oct 12, 2018 at 02:30:56PM +0300, Kirill A. Shutemov wrote:
> On Thu, Oct 11, 2018 at 06:37:56PM -0700, Joel Fernandes (Google) wrote:
> > @@ -239,7 +287,21 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
> >  			split_huge_pmd(vma, old_pmd, old_addr);
> >  			if (pmd_trans_unstable(old_pmd))
> >  				continue;
> > +		} else if (extent == PMD_SIZE) {
> 
> Hm. What guarantees that new_addr is PMD_SIZE-aligned?
> It's not obvious to me.

Ignore this :)

-- 
 Kirill A. Shutemov