From patchwork Tue Dec 19 19:29:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Kim, Dongwon" X-Patchwork-Id: 10124089 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id ACE966019C for ; Tue, 19 Dec 2017 19:38:05 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9F0232924D for ; Tue, 19 Dec 2017 19:38:05 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 93ACB2951E; Tue, 19 Dec 2017 19:38:05 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 360A02924D for ; Tue, 19 Dec 2017 19:38:05 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F1F856E35A; Tue, 19 Dec 2017 19:36:50 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4FC1C6E351 for ; Tue, 19 Dec 2017 19:36:40 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Dec 2017 11:36:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.45,428,1508828400"; d="scan'208";a="4018543" Received: from downor-z87x-ud5h.fm.intel.com ([10.1.122.11]) by orsmga007.jf.intel.com with ESMTP; 19 Dec 2017 11:36:39 -0800 From: Dongwon Kim To: linux-kernel@vger.kernel.org Subject: [RFC PATCH 20/60] hyper_dmabuf: optimized loop with less condition check Date: Tue, 19 Dec 2017 11:29:36 -0800 Message-Id: <1513711816-2618-20-git-send-email-dongwon.kim@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1513711816-2618-1-git-send-email-dongwon.kim@intel.com> References: <1513711816-2618-1-git-send-email-dongwon.kim@intel.com> MIME-Version: 1.0 Cc: xen-devel@lists.xenproject.org, mateuszx.potrola@intel.com, dri-devel@lists.freedesktop.org, dongwon.kim@intel.com X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP Redefined nents_last, which means # of gref in the last page of lvl2 table in any situation even if it is same as REFS_PER_PAGE. With this, loop can be simplified with less condition check. Signed-off-by: Dongwon Kim --- drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c b/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c index cc9860b..cb5b86f 100644 --- a/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c +++ b/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c @@ -184,8 +184,10 @@ struct page ** hyper_dmabuf_xen_map_shared_pages(int lvl3_gref, int domid, int n struct gnttab_map_grant_ref *data_map_ops; struct gnttab_unmap_grant_ref *data_unmap_ops; - int nents_last = nents % REFS_PER_PAGE; - int n_lvl2_grefs = (nents / REFS_PER_PAGE) + ((nents_last > 0) ? 1 : 0); + /* # of grefs in the last page of lvl2 table */ + int nents_last = (nents - 1) % REFS_PER_PAGE + 1; + int n_lvl2_grefs = (nents / REFS_PER_PAGE) + ((nents_last > 0) ? 1 : 0) - + (nents_last == REFS_PER_PAGE); int i, j, k; dev_dbg(hyper_dmabuf_private.device, "%s entry\n", __func__); @@ -270,7 +272,7 @@ struct page ** hyper_dmabuf_xen_map_shared_pages(int lvl3_gref, int domid, int n k = 0; - for (i = 0; i < (nents_last ? n_lvl2_grefs - 1 : n_lvl2_grefs); i++) { + for (i = 0; i < n_lvl2_grefs - 1; i++) { lvl2_table = pfn_to_kaddr(page_to_pfn(lvl2_table_pages[i])); for (j = 0; j < REFS_PER_PAGE; j++) { gnttab_set_map_op(&data_map_ops[k],