From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 08B4E6FA1 for ; Mon, 3 Apr 2023 14:26:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8472CC433D2; Mon, 3 Apr 2023 14:26:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1680532000; bh=NBPZGQ942ws4fxaQ3ieQb0lyvmMVEn7kAkRYh8pGsSk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jIz0BMm42MPH9+Rcal7GETAE+/LxL7DqGA5lVNL20IF3e5UFfAx2LfY6pO7zqIKET W9hZpdNSA7xm54rOfsdRvtsF5m73Uak1EaIeVkexFG0kUQ89P3eu5SbtQVlmQ2YVQt 8w8XF9yR2NGlGq8bpOAbl/MrWqAZtY9U0D9uHN8s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nathan Huckleberry , Eric Biggers Subject: [PATCH 5.10 081/173] fsverity: Remove WQ_UNBOUND from fsverity read workqueue Date: Mon, 3 Apr 2023 16:08:16 +0200 Message-Id: <20230403140417.044912385@linuxfoundation.org> X-Mailer: git-send-email 2.40.0 In-Reply-To: <20230403140414.174516815@linuxfoundation.org> References: <20230403140414.174516815@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Nathan Huckleberry commit f959325e6ac3f499450088b8d9c626d1177be160 upstream. WQ_UNBOUND causes significant scheduler latency on ARM64/Android. This is problematic for latency sensitive workloads, like I/O post-processing. Removing WQ_UNBOUND gives a 96% reduction in fsverity workqueue related scheduler latency and improves app cold startup times by ~30ms. WQ_UNBOUND was also removed from the dm-verity workqueue for the same reason [1]. This code was tested by running Android app startup benchmarks and measuring how long the fsverity workqueue spent in the runnable state. Before Total workqueue scheduler latency: 553800us After Total workqueue scheduler latency: 18962us [1]: https://lore.kernel.org/all/20230202012348.885402-1-nhuck@google.com/ Signed-off-by: Nathan Huckleberry Fixes: 8a1d0f9cacc9 ("fs-verity: add data verification hooks for ->readpages()") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230310193325.620493-1-nhuck@google.com Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman --- fs/verity/verify.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/fs/verity/verify.c +++ b/fs/verity/verify.c @@ -279,15 +279,15 @@ EXPORT_SYMBOL_GPL(fsverity_enqueue_verif int __init fsverity_init_workqueue(void) { /* - * Use an unbound workqueue to allow bios to be verified in parallel - * even when they happen to complete on the same CPU. This sacrifices - * locality, but it's worthwhile since hashing is CPU-intensive. + * Use a high-priority workqueue to prioritize verification work, which + * blocks reads from completing, over regular application tasks. * - * Also use a high-priority workqueue to prioritize verification work, - * which blocks reads from completing, over regular application tasks. + * For performance reasons, don't use an unbound workqueue. Using an + * unbound workqueue for crypto operations causes excessive scheduler + * latency on ARM64. */ fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue", - WQ_UNBOUND | WQ_HIGHPRI, + WQ_HIGHPRI, num_online_cpus()); if (!fsverity_read_workqueue) return -ENOMEM;