From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: Re: [PATCH 2/4] mm: speed up mremap by 500x on large regions (v2) Date: Wed, 24 Oct 2018 19:13:50 -0700 Message-ID: <20181025021350.GB13560@joelaf.mtv.corp.google.com> References: <20181013013200.206928-1-joel@joelfernandes.org> <20181013013200.206928-3-joel@joelfernandes.org> <20181024101255.it4lptrjogalxbey@kshutemo-mobl1> <20181024115733.GN8537@350D> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=jB8RpTc7IAIoNhq2EERqIuaS843hm/hgSbs5gYFYvOc=; b=qyy95DWskV8RS+ ixreCwCcs7yWnY/gW5ur8iJCy4kPhreIfFNEMoaP/0RnD4FonlQmlAZ8umpbCCy/MIEDL+fj1Bcg9 EjwyeLC/e8+mALe6mi4TGSTvI5JXT8LEkZMZwYK5XtAQxbLuab9Esn0STYtZJ1IHs+XDTA/IB96FM pl1n7M77ED7EXxeKoOQWNXFZvQ//ymkjGXOlY3OMdVSTokxCwiiP39yGbOaijmjxodcarDGKdo2Zw ZPunvzWEiUcsIkXHmqY5R7jDALgyAfu6fVqdAtbLTn1GrMYyAAY4QWdLmfI9v9xxuomBFJxNWEc4M y8D9Kci7BWwohw747Tcg==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=5CbWcmgaWhK69oh2DEOguVgA2uKl1YpKoqaGwtGwge8=; b=q/q3QTdACzUlPpDQMN1kjcezMfcsn0Yv6fXB6ODPHDCxjW91L/KWd7ad+HnYMhVDLK 4w8FEyzAp+rB09Si8JZs7MJE9NTlxjm6PO3Hk2MpIdxGl6P2KagjiLkUB/ExO2oGujpm CSZTqm0K2zOVm+Foil/VJrYg2JhZozpJsR9l8= Content-Disposition: inline In-Reply-To: <20181024115733.GN8537@350D> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+gla-linux-snps-arc=m.gmane.org@lists.infradead.org To: Balbir Singh Cc: linux-mips@linux-mips.org, Rich Felker , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , Catalin Marinas , Dave Hansen , Will Deacon , 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 , kvmarm@lists.cs.columbia.edu, dancol@google.com, Yoshinori Sato , linux-xtensa@linux-xtensa.org, linux-hexagon@vger.kernel.org, Helge Deller , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , hughd@google.com, "James E.J. Bottomley" , kasan-dev@googlegroups.com, anton.ivanov@kot-begemot.co.uk, Ingo Molnar , Geert 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). - Joel