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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A906CDB47E for ; Thu, 12 Oct 2023 02:10:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234014AbjJLCGv (ORCPT ); Wed, 11 Oct 2023 22:06:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49442 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233794AbjJLCGu (ORCPT ); Wed, 11 Oct 2023 22:06:50 -0400 Received: from wxsgout04.xfusion.com (wxsgout04.xfusion.com [36.139.87.180]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C441F98; Wed, 11 Oct 2023 19:06:46 -0700 (PDT) Received: from wuxshcsitd00600.xfusion.com (unknown [10.32.133.213]) by wxsgout04.xfusion.com (SkyGuard) with ESMTPS id 4S5Xxw36Vvz9y7xl; Thu, 12 Oct 2023 10:04:20 +0800 (CST) Received: from localhost (10.82.147.3) by wuxshcsitd00600.xfusion.com (10.32.133.213) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Thu, 12 Oct 2023 10:06:40 +0800 Date: Thu, 12 Oct 2023 10:06:40 +0800 From: Wang Jinchao To: Steffen Klassert , Daniel Jordan , , CC: Subject: [RFC v2] padata: Simplify sysfs cpumask and sequencing logic Message-ID: <202310121006-wangjinchao@xfusion.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline X-Originating-IP: [10.82.147.3] X-ClientProxiedBy: wuxshcsitd00603.xfusion.com (10.32.134.231) To wuxshcsitd00600.xfusion.com (10.32.133.213) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I've identified several potential optimizations for padata. I'd appreciate it if you could take a look at my ideas to see if they are feasible. Utilizing the WQ_SYSFS from workqueue to support sysfs ====================================================== Padata relies on workqueue, and since workqueue has already implemented support for cpumask through WQ_SYSFS, we can reuse this functionality and avoid redundant implementation. Link: https://docs.kernel.org/core-api/workqueue.html#affinity-scopes Using completion to ensure the sequencing of the 'serial()' =========================================================== In the current implementation, to ensure the sequencing of 'serial()', we've used seq_nr, reorder_list, padata_serial_queue, reorder_work... which has made the logic quite complex. These operations can be simplified by using 'completion'. Specifically: 1. in padata_do_parallel() 1. init_completion(parallel_done) **before** queue_work 2. queue_work(serial_work) 2. in padata_parallel_worker 1. complete(parallel_done) **after** parallel(padata) 3. in padata_serial_worker 1. wait_for_completion(parallel_done) **before** serial(padata) Here's a simplified code snippet: ```c struct padata_priv { struct completion parallel_done; struct work_struct parallel_work; struct work_struct serial_work; void (*parallel)(struct padata_priv *padata); void (*serial)(struct padata_priv *padata); } void padata_do_parallel(struct padata_priv *padata) { ... init_completion(&padata->parallel_done); queue_work(pinst->serial_wq, &padata->serial_work); queue_work(pinst->parallel_wq, &padata->parallel_work); ... } static void padata_parallel_worker(struct work_struct *parallel_work) { struct padata_priv *padata = container_of(parallel_work, struct padata_priv, parallel_work); padata->parallel(padata); // notify serial_worker to do serial() complete(&padata->parallel_done); } static void padata_serial_worker(struct work_struct *serial_work) { struct padata_priv *padata = container_of(serial_work, struct padata_priv, serial_work); wait_for_completion(&padata->parallel_done); padata->serial(padata); } ```