From patchwork Tue Aug 6 00:46:47 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Yang X-Patchwork-Id: 11078003 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9C73B17E0 for ; Tue, 6 Aug 2019 00:48:14 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7DDF52899B for ; Tue, 6 Aug 2019 00:48:14 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6002A28999; Tue, 6 Aug 2019 00:48:14 +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=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id EAE8B2897D for ; Tue, 6 Aug 2019 00:48:13 +0000 (UTC) Received: from localhost ([::1]:57874 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hune9-0000QS-B6 for patchwork-qemu-devel@patchwork.kernel.org; Mon, 05 Aug 2019 20:48:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39758) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hundM-0007wJ-K6 for qemu-devel@nongnu.org; Mon, 05 Aug 2019 20:47:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hundL-0002KL-KC for qemu-devel@nongnu.org; Mon, 05 Aug 2019 20:47:24 -0400 Received: from mga03.intel.com ([134.134.136.65]:38671) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hundL-0002Jy-Cw for qemu-devel@nongnu.org; Mon, 05 Aug 2019 20:47:23 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Aug 2019 17:47:22 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,350,1559545200"; d="scan'208";a="202637806" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 05 Aug 2019 17:47:21 -0700 From: Wei Yang To: qemu-devel@nongnu.org Date: Tue, 6 Aug 2019 08:46:47 +0800 Message-Id: <20190806004648.8659-2-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190806004648.8659-1-richardw.yang@linux.intel.com> References: <20190806004648.8659-1-richardw.yang@linux.intel.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 134.134.136.65 Subject: [Qemu-devel] [PATCH 1/2] migration/postcopy: simplify calculation of run_start and fixup_start_addr X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Wei Yang , dgilbert@redhat.com, quintela@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP The purpose of the calculation is to find a HostPage which is partially dirty. * fixup_start_addr points to the start of the HostPage to discard * run_start points to the next HostPage to check While in the middle stage, there would two cases for run_start: * aligned with HostPage means this is not partially dirty * not aligned means this is partially dirty When it is aligned, no work and calculation is necessary. run_start already points to the start of next HostPage and is ready to continue. When it is not aligned, the calculation could be simplified with: * fixup_start_addr = QEMU_ALIGN_DOWN(run_start, host_ratio) * run_start = QEMU_ALIGN_UP(run_start, host_ratio) By doing so, run_start always points to the next HostPage to check. fixup_start_addr always points to the HostPage to discard. Signed-off-by: Wei Yang Reviewed-by: Dr. David Alan Gilbert --- migration/ram.c | 34 +++++++--------------------------- 1 file changed, 7 insertions(+), 27 deletions(-) diff --git a/migration/ram.c b/migration/ram.c index c9585487ac..d86661a015 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -2956,7 +2956,6 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, } while (run_start < pages) { - unsigned long fixup_start_addr; unsigned long host_offset; /* @@ -2964,45 +2963,26 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, * page, then we need to fixup this host page. */ host_offset = run_start % host_ratio; - if (host_offset) { - fixup_start_addr = run_start - host_offset; - /* - * This host page has gone, the next loop iteration starts - * from after the fixup - */ - run_start = fixup_start_addr + host_ratio; - } else { + if (!host_offset) { /* Find the end of this run */ - unsigned long run_end; if (unsent_pass) { - run_end = find_next_bit(unsentmap, pages, run_start + 1); + run_start = find_next_bit(unsentmap, pages, run_start + 1); } else { - run_end = find_next_zero_bit(bitmap, pages, run_start + 1); + run_start = find_next_zero_bit(bitmap, pages, run_start + 1); } /* * If the end isn't at the start of a host page, then the * run doesn't finish at the end of a host page * and we need to discard. */ - host_offset = run_end % host_ratio; - if (host_offset) { - fixup_start_addr = run_end - host_offset; - /* - * This host page has gone, the next loop iteration starts - * from after the fixup - */ - run_start = fixup_start_addr + host_ratio; - } else { - /* - * No discards on this iteration, next loop starts from - * next sent/dirty page - */ - run_start = run_end + 1; - } + host_offset = run_start % host_ratio; } if (host_offset) { unsigned long page; + unsigned long fixup_start_addr = QEMU_ALIGN_DOWN(run_start, + host_ratio); + run_start = QEMU_ALIGN_UP(run_start, host_ratio); /* Tell the destination to discard this page */ if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) {