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=-1.0 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 470ADC04EBF for ; Wed, 5 Dec 2018 00:43:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 104A02081C for ; Wed, 5 Dec 2018 00:43:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 104A02081C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com 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 S1726748AbeLEAnB (ORCPT ); Tue, 4 Dec 2018 19:43:01 -0500 Received: from mga04.intel.com ([192.55.52.120]:44396 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725904AbeLEAm4 (ORCPT ); Tue, 4 Dec 2018 19:42:56 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Dec 2018 16:42:56 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,316,1539673200"; d="scan'208";a="98694711" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.137]) by orsmga008.jf.intel.com with ESMTP; 04 Dec 2018 16:42:57 -0800 Received: by tassilo.localdomain (Postfix, from userid 1000) id E699D300F9B; Tue, 4 Dec 2018 16:42:55 -0800 (PST) From: Andi Kleen To: Larry Bassel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: RFC: revisiting shared page tables References: <20181204231623.GA19227@ubuette> Date: Tue, 04 Dec 2018 16:42:55 -0800 In-Reply-To: <20181204231623.GA19227@ubuette> (Larry Bassel's message of "Tue, 4 Dec 2018 15:16:24 -0800") Message-ID: <87y3947qi8.fsf@linux.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Larry Bassel writes: > > Isn't Linux kernel archaeology fun :-) > > 13 years have elapsed. Given the many changes in the kernel since the original > patch submission, I'd appreciate your insight into the following questions: I believe the main objection (from Linus) back then that it would complicate page table locking significantly, and also add overhead for it. If anything locking (or even lack of locking, as in lockless code) has gotten far more hairy in the 13 years, so this issue likely got far worse. So if you would work on it I would start with some investigation what the locking scheme would take, how maintainable it would be, and how many atomics in hot paths it would add. -Andi