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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D63DEC4727F for ; Tue, 29 Sep 2020 03:50:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7D3C21548 for ; Tue, 29 Sep 2020 03:50:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727301AbgI2DuW (ORCPT ); Mon, 28 Sep 2020 23:50:22 -0400 Received: from mga12.intel.com ([192.55.52.136]:47132 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726944AbgI2DuV (ORCPT ); Mon, 28 Sep 2020 23:50:21 -0400 IronPort-SDR: rmBSY0RNXPljD9k+8ct1CYYtHfZtmaxSIXNzZno7tG2spfwcTSRlLVwDZC6vV8hEI7pLz3xUcC 3VUvNys7pwyQ== X-IronPort-AV: E=McAfee;i="6000,8403,9758"; a="141509992" X-IronPort-AV: E=Sophos;i="5.77,316,1596524400"; d="scan'208";a="141509992" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Sep 2020 20:50:21 -0700 IronPort-SDR: 4hkITZZ/K0G4MetaEbwAE6Nxw48gyIYvzAyAYdal1lP/MXST6Zu1rdbbIxBs7Qt9trstIqwZj8 P5RkZYML9mXg== X-IronPort-AV: E=Sophos;i="5.77,316,1596524400"; d="scan'208";a="488901368" Received: from jlasecki-mobl2.ger.corp.intel.com (HELO localhost) ([10.252.49.78]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Sep 2020 20:50:14 -0700 Date: Tue, 29 Sep 2020 06:50:10 +0300 From: Jarkko Sakkinen To: Sean Christopherson 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: <20200929035010.GB301037@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200929011438.GA31167@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? /Jarkko