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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 9DADFC4727F for ; Tue, 29 Sep 2020 08:35:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6098320897 for ; Tue, 29 Sep 2020 08:35:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727768AbgI2Ifc (ORCPT ); Tue, 29 Sep 2020 04:35:32 -0400 Received: from mga14.intel.com ([192.55.52.115]:44863 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725535AbgI2Ifc (ORCPT ); Tue, 29 Sep 2020 04:35:32 -0400 IronPort-SDR: NsYEVSA57OkvwXSDYcdQjyll6lGyXsK+UYo0nu+GCytTBVTbATLjmUIMoWgEFxATw6powPH+YN zi8Z0VwqLZqQ== X-IronPort-AV: E=McAfee;i="6000,8403,9758"; a="161371984" X-IronPort-AV: E=Sophos;i="5.77,317,1596524400"; d="scan'208";a="161371984" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Sep 2020 01:35:31 -0700 IronPort-SDR: UgLzSefUspPCRspHRQgyPO1tTCeV29f13AFZwPfkybz0UPN9MKI0TxsE4oe0T0uEB8aYLkGBoe 1sfjMFQPjf0Q== X-IronPort-AV: E=Sophos;i="5.77,317,1596524400"; d="scan'208";a="345191068" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.160]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Sep 2020 01:35:30 -0700 Date: Tue, 29 Sep 2020 01:35:28 -0700 From: Sean Christopherson To: Jarkko Sakkinen Cc: Borislav Petkov , x86@kernel.org, linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jethro Beekman , Jordan Hand , Nathaniel McCallum , Chunyang Hui , Seth Moore , akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com, asapek@google.com, cedric.xing@intel.com, chenalexchen@google.com, conradparker@google.com, cyhanish@google.com, dave.hansen@intel.com, haitao.huang@intel.com, josh@joshtriplett.org, kai.huang@intel.com, kai.svahn@intel.com, kmoy@google.com, ludloff@google.com, luto@kernel.org, nhorman@redhat.com, puiterwijk@redhat.com, rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com Subject: Re: [PATCH v38 16/24] x86/sgx: Add a page reclaimer Message-ID: <20200929083528.GN353@linux.intel.com> References: <20200915112842.897265-1-jarkko.sakkinen@linux.intel.com> <20200915112842.897265-17-jarkko.sakkinen@linux.intel.com> <20200922104538.GE22660@zn.tnic> <20200922140314.GA164527@linux.intel.com> <20200929011438.GA31167@linux.intel.com> <20200929035010.GB301037@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200929035010.GB301037@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 29, 2020 at 06:50:10AM +0300, Jarkko Sakkinen wrote: > On Mon, Sep 28, 2020 at 06:14:39PM -0700, Sean Christopherson wrote: > > On Tue, Sep 22, 2020 at 05:03:23PM +0300, Jarkko Sakkinen wrote: > > > On Tue, Sep 22, 2020 at 12:45:38PM +0200, Borislav Petkov wrote: > > > > > + spin_lock(&sgx_active_page_list_lock); > > > > > + for (i = 0; i < SGX_NR_TO_SCAN; i++) { > > > > > + if (list_empty(&sgx_active_page_list)) > > > > > > > > Isn't it enough to do this once, i.e., not in the loop? You're holding > > > > sgx_active_page_list_lock... > > > > Argh, I missed this until I looked at Jarkko's updated tree. > > > > The reason for checking list_empty() on every iteration is that the loop is > > greedy, i.e. it tries to grab and reclaim up to 16 (SGX_NR_TO_SCAN) EPC pages > > at a time. > > > > > I think that would make sense. Distantly analogous to the EINIT > > > discussion. Too complex code for yet to be known problem workloads I'd > > > say. > > > > Nooooo. Please no. > > I added this comment in the beginning of the sgx_reclaim_pages() based > on your response: > > /* > * Take a fixed number of pages from the head of the active page pool and > * reclaim them to the enclave's private shmem files. Skip the pages, which have > * been accessed since the last scan. Move those pages to the tail of active > * page pool so that the pages get scanned in LRU like fashion. > * > * Batch process a chunk of pages (at the moment 16) in order to degrade amount > * of IPI's and ETRACK's potentially required. sgx_encl_ewb() does degrade a bit > * among the HW threads with three stage EWB pipeline (EWB, ETRACK + EWB and IPI > * + EWB) but not sufficiently. Reclaiming one page at a time would also be > * problematic as it would increase the lock contention too much, which would > * halt forward progress. > */ > > And reverted reclaimer patch as it was. Do you have anything in mind > that I should add or modify in it? Nope, can't think of anything.