From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 631D8ECDE46 for ; Wed, 31 Oct 2018 09:30:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24D0E20840 for ; Wed, 31 Oct 2018 09:30:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="jY8arnAl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 24D0E20840 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727950AbeJaS1b (ORCPT ); Wed, 31 Oct 2018 14:27:31 -0400 Received: from merlin.infradead.org ([205.233.59.134]:34858 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727597AbeJaS1b (ORCPT ); Wed, 31 Oct 2018 14:27:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3jes58u1jTxmuOF8FMhmEDRdUkFP9Qkm++im5XLV5ys=; b=jY8arnAl+D3zGHGTnlVl9fRINf 0r1qffbbaW9tzevjDNcuLMs29ffRTn85xFLvU6m15urgYyQQF0NVmBRd3mTeQps+9jOn+LQZSz8th pQ9qe85dgObjx+EzzI2vfdYSD4xlHYw4nsgyLEdfqO8stcKrJUL/ywEI4ZfdOiTHcKplk8Vp5BIU2 QjfTR3C+gjZk9IIk9Eh6V4M6qbLokd0V/dY7XwKEAHL3FQ5aeP/yhFMUXBygnusbhuAi5bbiuSR/2 DbOWIzFiRCvk8ikqZF78waI5gkJiEkOGKvl9bBUSKIF1eelCR0wpbSTvdVNEVdmNoCQAp0cABhfhW /9+Xy3Ag==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gHmoq-0002Sf-7w; Wed, 31 Oct 2018 09:29:44 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 36EB42029FA14; Wed, 31 Oct 2018 10:29:42 +0100 (CET) Date: Wed, 31 Oct 2018 10:29:42 +0100 From: Peter Zijlstra To: Matthew Wilcox Cc: Andy Lutomirski , nadav.amit@gmail.com, Kees Cook , Igor Stoppa , Mimi Zohar , Dave Chinner , James Morris , Michal Hocko , Kernel Hardening , linux-integrity , linux-security-module , Igor Stoppa , Dave Hansen , Jonathan Corbet , Laura Abbott , Randy Dunlap , Mike Rapoport , "open list:DOCUMENTATION" , LKML , Thomas Gleixner Subject: Re: [PATCH 10/17] prmem: documentation Message-ID: <20181031092942.GJ744@hirez.programming.kicks-ass.net> References: <20181026092609.GB3159@worktop.c.hoisthospitality.com> <20181028183126.GB744@hirez.programming.kicks-ass.net> <40cd77ce-f234-3213-f3cb-0c3137c5e201@gmail.com> <20181030152641.GE8177@hirez.programming.kicks-ass.net> <0A7AFB50-9ADE-4E12-B541-EC7839223B65@amacapital.net> <20181030175814.GB10491@bombadil.infradead.org> <28C8CD2A-BDC0-49A5-854E-1E18968528B8@amacapital.net> <20181030212551.GD10491@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20181030212551.GD10491@bombadil.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 30, 2018 at 02:25:51PM -0700, Matthew Wilcox wrote: > On Tue, Oct 30, 2018 at 11:51:17AM -0700, Andy Lutomirski wrote: > > Finally, one issue: rare_alloc() is going to utterly suck > > performance-wise due to the global IPI when the region gets zapped out > > of the direct map or otherwise made RO. This is the same issue that > > makes all existing XPO efforts so painful. We need to either optimize > > the crap out of it somehow or we need to make sure it’s not called > > except during rare events like device enumeration. > > Batching operations is kind of the whole point of the VM ;-) Either > this rare memory gets used a lot, in which case we'll want to create slab > caches for it, make it a MM zone and the whole nine yeards, or it's not > used very much in which case it doesn't matter that performance sucks. Yes, for the dynamic case something along those lines would be needed. If we have a single rare zone, we could even have __GFP_RARE or whatever that manages this. The page allocator would have to grow a rare memblock type, and every rare alloc would allocate from a rare memblock, when none is available, creation of a rare block would set up the mappings etc.. > For now, I'd suggest allocating 2MB chunks as needed, and having a > shrinker to hand back any unused pieces. Something like the percpu allocator?