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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 26409CDB470 for ; Fri, 14 Nov 2025 02:13:01 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vJjIH-0003GU-SA; Thu, 13 Nov 2025 21:12:09 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vJjIG-0003D4-5Q; Thu, 13 Nov 2025 21:12:08 -0500 Received: from smtp-pop-umt-2.cecloud.com ([1.203.97.240] helo=smtp.cecloud.com) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vJjIE-0003DW-KH; Thu, 13 Nov 2025 21:12:07 -0500 Received: from localhost (localhost [127.0.0.1]) by smtp.cecloud.com (Postfix) with ESMTP id 5844C900117; Fri, 14 Nov 2025 10:12:04 +0800 (CST) X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-SKE-CHECKED: 1 X-ANTISPAM-LEVEL: 2 Received: from localhost.localdomain (unknown [111.48.69.245]) by smtp.cecloud.com (postfix) whith ESMTP id P506955T281463492637040S1763086293564791_; Fri, 14 Nov 2025 10:12:04 +0800 (CST) X-IP-DOMAINF: 1 X-RL-SENDER: luzhipeng@cestc.cn X-SENDER: luzhipeng@cestc.cn X-LOGIN-NAME: luzhipeng@cestc.cn X-FST-TO: qemu-block@nongnu.org X-RCPT-COUNT: 6 X-LOCAL-RCPT-COUNT: 1 X-MUTI-DOMAIN-COUNT: 0 X-SENDER-IP: 111.48.69.245 X-ATTACHMENT-NUM: 0 X-UNIQUE-TAG: <04a5a6d7d3eff6906be846f3d51141b0> X-System-Flag: 0 From: luzhipeng To: qemu-block@nongnu.org Cc: Alberto Garcia , Kevin Wolf , Hanna Reitz , qemu-devel@nongnu.org, luzhipeng Subject: [PATCH] mirror: Optimize mirroring for zero blocks in mirror_read_complete Date: Fri, 14 Nov 2025 10:11:10 +0800 Message-ID: <20251114021110.1464-2-luzhipeng@cestc.cn> X-Mailer: git-send-email 2.45.1.windows.1 In-Reply-To: <20251114021110.1464-1-luzhipeng@cestc.cn> References: <20251114021110.1464-1-luzhipeng@cestc.cn> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: permerror client-ip=1.203.97.240; envelope-from=luzhipeng@cestc.cn; helo=smtp.cecloud.com X-Spam_score_int: -14 X-Spam_score: -1.5 X-Spam_bar: - X-Spam_report: (-1.5 / 5.0 requ) BAYES_00=-1.9, KHOP_HELO_FCRDNS=0.398, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, T_SPF_PERMERROR=0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org When mirroring data blocks, detect if the read data consists entirely of zeros. If so, use blk_co_pwrite_zeroes() instead of regular write to improve performance. Signed-off-by: luzhipeng --- block/mirror.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/block/mirror.c b/block/mirror.c index b344182c74..535112f65d 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -269,6 +269,33 @@ static void coroutine_fn mirror_read_complete(MirrorOp *op, int ret) return; } + /* Check if the read data is all zeros */ + bool is_zero = true; + for (int i = 0; i < op->qiov.niov; i++) { + if (!buffer_is_zero(op->qiov.iov[i].iov_base, + op->qiov.iov[i].iov_len)) { + is_zero = false; + break; + } + } + + /* Write to target - optimized path for zero blocks */ + if (is_zero) { + /* + * Use zero-writing interface which may: + * 1. Avoid actual data transfer + * 2. Enable storage-level optimizations + * 3. Potentially unmap blocks (if supported) + */ + ret = blk_co_pwrite_zeroes(s->target, op->offset, + op->qiov.size, + BDRV_REQ_MAY_UNMAP); + } else { + /* Normal data write path */ + ret = blk_co_pwritev(s->target, op->offset, + op->qiov.size, &op->qiov, 0); + } + ret = blk_co_pwritev(s->target, op->offset, op->qiov.size, &op->qiov, 0); mirror_write_complete(op, ret); } -- 2.45.1.windows.1