From patchwork Tue Feb 25 22:48:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Iooss X-Patchwork-Id: 11404879 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DCFAA14BC for ; Tue, 25 Feb 2020 22:48:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5BE120732 for ; Tue, 25 Feb 2020 22:48:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728889AbgBYWsy (ORCPT ); Tue, 25 Feb 2020 17:48:54 -0500 Received: from mx1.polytechnique.org ([129.104.30.34]:32892 "EHLO mx1.polytechnique.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728865AbgBYWsy (ORCPT ); Tue, 25 Feb 2020 17:48:54 -0500 Received: from localhost.localdomain (85-168-38-217.rev.numericable.fr [85.168.38.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ssl.polytechnique.org (Postfix) with ESMTPSA id E37FE561296 for ; Tue, 25 Feb 2020 23:48:50 +0100 (CET) From: Nicolas Iooss To: selinux@vger.kernel.org Subject: [PATCH 1/1] libsepol: make ebitmap_cardinality() of linear complexity Date: Tue, 25 Feb 2020 23:48:41 +0100 Message-Id: <20200225224841.2693481-1-nicolas.iooss@m4x.org> X-Mailer: git-send-email 2.25.0 MIME-Version: 1.0 X-AV-Checked: ClamAV using ClamSMTP at svoboda.polytechnique.org (Tue Feb 25 23:48:51 2020 +0100 (CET)) X-Spam-Flag: No, tests=bogofilter, spamicity=0.000000, queueID=3AB30561299 X-Org-Mail: nicolas.iooss.2010@polytechnique.org Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org As ebitmap_get_bit() complexity is linear in the size of the bitmap, the complexity of ebitmap_cardinality() is quadratic. This can be optimized by browsing the nodes of the bitmap directly in ebitmap_cardinality(). While at it, use built-in function __builtin_popcountll() to count the ones in the 64-bit value n->map for each bitmap node. This seems better suited than "count++". This seems to work on gcc and clang on x86, x86_64, ARM and ARM64 but if it causes compatibility issues with some compilers or architectures (or with older versions of gcc or clang), the use of __builtin_popcountll() can be replaced by a C implementation of a popcount algorithm. Signed-off-by: Nicolas Iooss Acked-by: Ondrej Mosnacek --- libsepol/src/ebitmap.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/libsepol/src/ebitmap.c b/libsepol/src/ebitmap.c index d23444ce5064..a5108b7184c5 100644 --- a/libsepol/src/ebitmap.c +++ b/libsepol/src/ebitmap.c @@ -128,14 +128,15 @@ int ebitmap_andnot(ebitmap_t *dst, ebitmap_t *e1, ebitmap_t *e2, unsigned int ma unsigned int ebitmap_cardinality(ebitmap_t *e1) { - unsigned int i, count = 0; + unsigned int count = 0; + ebitmap_node_t *n; if (e1->cardinality || e1->highbit == 0) return e1->cardinality; - for (i=ebitmap_startbit(e1); i < ebitmap_length(e1); i++) - if (ebitmap_get_bit(e1, i)) - count++; + for (n = e1->node; n; n = n->next) { + count += __builtin_popcountll(n->map); + } e1->cardinality = count; return count; }