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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 AFE23C433F4 for ; Mon, 27 Aug 2018 08:49:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74925208B2 for ; Mon, 27 Aug 2018 08:49:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74925208B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.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 S1727230AbeH0MfQ (ORCPT ); Mon, 27 Aug 2018 08:35:16 -0400 Received: from gate.crashing.org ([63.228.1.57]:59045 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726802AbeH0MfQ (ORCPT ); Mon, 27 Aug 2018 08:35:16 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id w7R89p6x007276; Mon, 27 Aug 2018 03:09:52 -0500 Message-ID: <4ef8a2aa44db971340b0bcc4f73d639455dd4282.camel@kernel.crashing.org> Subject: Re: [PATCH 3/4] mm/tlb, x86/mm: Support invalidating TLB caches for RCU_TABLE_FREE From: Benjamin Herrenschmidt To: Nicholas Piggin , Peter Zijlstra Cc: Will Deacon , Linus Torvalds , Andrew Lutomirski , the arch/x86 maintainers , Borislav Petkov , Rik van Riel , Jann Horn , Adin Scannell , Dave Hansen , Linux Kernel Mailing List , linux-mm , David Miller , Martin Schwidefsky , Michael Ellerman Date: Mon, 27 Aug 2018 18:09:50 +1000 In-Reply-To: <20180827180458.4af9b2ac@roar.ozlabs.ibm.com> References: <20180822155527.GF24124@hirez.programming.kicks-ass.net> <20180823134525.5f12b0d3@roar.ozlabs.ibm.com> <776104d4c8e4fc680004d69e3a4c2594b638b6d1.camel@au1.ibm.com> <20180823133958.GA1496@brain-police> <20180824084717.GK24124@hirez.programming.kicks-ass.net> <20180824113214.GK24142@hirez.programming.kicks-ass.net> <20180824113953.GL24142@hirez.programming.kicks-ass.net> <20180827150008.13bce08f@roar.ozlabs.ibm.com> <20180827074701.GW24124@hirez.programming.kicks-ass.net> <20180827180458.4af9b2ac@roar.ozlabs.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-1.fc28) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2018-08-27 at 18:04 +1000, Nicholas Piggin wrote: > > Yes.. I see that. tlb_remove_check_page_size_change() really is a rather > > ugly thing, it can cause loads of TLB flushes. Do you really _have_ to > > do that? The way ARM and x86 work is that using INVLPG in a 4K stride is > > still correct for huge pages, inefficient maybe, but so is flushing > > every other page because 'sparse' transparant-huge-pages. > > It could do that. It requires a tlbie that matches the page size, > so it means 3 sizes. I think possibly even that would be better > than current code, but we could do better if we had a few specific > fields in there. More tlbies ? With the cost of the broadasts on the fabric ? I don't think so.. or I'm not understanding your point... Sadly our architecture requires a precise match between the page size specified in the tlbie instruction and the entry in the TLB or it won't be flushed. Ben.