From mboxrd@z Thu Jan  1 00:00:00 1970
From: Balbir Singh <bsingharora@gmail.com>
Subject: Re: [PATCH 2/4] mm: speed up mremap by 500x on large regions (v2)
Date: Sat, 27 Oct 2018 21:21:02 +1100
Message-ID: <20181027102102.GO8537@350D>
References: <20181013013200.206928-1-joel@joelfernandes.org>
 <20181013013200.206928-3-joel@joelfernandes.org>
 <20181024101255.it4lptrjogalxbey@kshutemo-mobl1>
 <20181024115733.GN8537@350D>
 <20181025021350.GB13560@joelaf.mtv.corp.google.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Cc: linux-mips@linux-mips.org, Rich Felker <dalias@libc.org>,
 linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
 Peter Zijlstra <peterz@infradead.org>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Dave Hansen <dave.hansen@linux.intel.com>, Will Deacon <will.deacon@arm.com>,
 mhocko@kernel.org, linux-mm@kvack.org, lokeshgidra@google.com,
 sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org,
 elfring@users.sourceforge.net, Jonas Bonn <jonas@southpole.se>,
 kvmarm@lists.cs.columbia.edu, dancol@google.com,
 Yoshinori Sato <ysato@users.sourceforge.jp>, linux-xtensa@linux-xtensa.org,
 linux-hexagon@vger.kernel.org, Helge Deller <deller@gmx.de>,
 "maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" <x86@kernel.org>,
 hughd@google.com, "James E.J. Bottomley" <jejb@parisc-linux.org>,
 kasan-dev@googlegroups.com, anton.ivanov@kot-begemot.co.uk,
 Ingo Molnar <mingo@redhat.com>, Geert Uy
To: Joel Fernandes <joel@joelfernandes.org>
Return-path: <linux-snps-arc-bounces+gla-linux-snps-arc=m.gmane.org@lists.infradead.org>
In-Reply-To: <20181025021350.GB13560@joelaf.mtv.corp.google.com>
List-Id: Linux on Synopsys ARC Processors <linux-snps-arc.lists.infradead.org>
List-Unsubscribe: <http://lists.infradead.org/mailman/options/linux-snps-arc>,
 <mailto:linux-snps-arc-request@lists.infradead.org?subject=unsubscribe>
List-Archive: <http://lists.infradead.org/pipermail/linux-snps-arc/>
List-Post: <mailto:linux-snps-arc@lists.infradead.org>
List-Help: <mailto:linux-snps-arc-request@lists.infradead.org?subject=help>
List-Subscribe: <http://lists.infradead.org/mailman/listinfo/linux-snps-arc>,
 <mailto:linux-snps-arc-request@lists.infradead.org?subject=subscribe>
Errors-To: linux-snps-arc-bounces+gla-linux-snps-arc=m.gmane.org@lists.infradead.org

On Wed, Oct 24, 2018 at 07:13:50PM -0700, Joel Fernandes wrote:
> On Wed, Oct 24, 2018 at 10:57:33PM +1100, Balbir Singh wrote:
> [...]
> > > > +		pmd_t pmd;
> > > > +
> > > > +		new_ptl = pmd_lockptr(mm, new_pmd);
> > 
> > 
> > Looks like this is largely inspired by move_huge_pmd(), I guess a lot of
> > the code applies, why not just reuse as much as possible? The same comments
> > w.r.t mmap_sem helping protect against lock order issues applies as well.
> 
> I thought about this and when I looked into it, it seemed there are subtle
> differences that make such sharing not worth it (or not possible).
>

Could you elaborate on them?

Thanks,
Balbir Singh.