From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh 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" 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=WOxIW/nPLy7Rt0f4i3YQkVCRVK7+S3eEt3luQqHVr8g=; b=Xi/S0xTc10L/3b cV2vG9fZHyqaYQVCKdzQKJ/ChAOGHXc6Hc4P8sb5ZR2pUYF+Dazwg+NoUKyfZo/OqsLY7Yn8zoMT6 mi/IuP0OWXpP/xFy/trW39QcUJ75H8wHv9bIYHfZsomztCAXNeZNkprjxYEKUcwhM8Fa8RITdZb7h lnzddadVn73vuzn8vJPVV69e3AYqIOqL1znRgXF3cZJ0zKCgmBtnpXqhw2tXar8T+l0F3vz+TuysU 5i1+82jZaOkqCdTVK76dHzkHlvUvNzBRPj8qdoVmVNmh09f25mOgUAuhkj3zc4MfPqSE0OgG12Cs4 ZsxBoyZZU0bY1lpJzWOg==; DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Ytoc7E/E+CDN+36oMCq4ib7UWrIKwi1XigueqliThJE=; b=ab1knh/8i2Gpv4Vxfi+YDSBKbX/LgufE79cYPr5GJEdQUVQbI970thsDIy0ZjV1q0k ZSfcWvh4GTM9Brshk9p+y4tQ9MlVv9xCOgRN+Mkl3IacQhaurmJjOF4ISMav3UWSPWT0 QDI4JUUMAIPA35q0/cXsitIc3ySa7+/5ANkq6TLz2UHPpSbIN1fzgNHsIaIbSC3XX++1 mylMnA2ff0XDd2sL+yXZDHQHXijLBXi1MJNMHNoE52RFFgyL7H1Hr53le1mRs/9vRlLJ 8fln4V5coK7PbseEtgyE6znLwjAsimR/DLzPXzQyaRXpcBZcO/1WMqn8CO3ILrNZhl0z +0sw== Content-Disposition: inline In-Reply-To: <20181025021350.GB13560@joelaf.mtv.corp.google.com> 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: Joel Fernandes 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 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.