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 8DBF5C433EF for ; Thu, 13 Jan 2022 16:37:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230234AbiAMQhv (ORCPT ); Thu, 13 Jan 2022 11:37:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229515AbiAMQht (ORCPT ); Thu, 13 Jan 2022 11:37:49 -0500 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33B23C061574 for ; Thu, 13 Jan 2022 08:37:49 -0800 (PST) Received: by mail-pl1-x630.google.com with SMTP id c3so10644479pls.5 for ; Thu, 13 Jan 2022 08:37:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=bVTXmmIE7IBPyxQrXnC0p71oDoaSop9Sc+enhFol2Bo=; b=dhTbt7MQvjKFdG3Q5P8q2KbFg1viclCrADmfZsOk0AMqMAnNr1pS6PUERVLcmCKcJ1 yLpTg0aYXMSBHA5M9Cjv8Ln+skHkL2cmHUkzz1uJ+fAe+zXlMl57Edx6aa4LzIB+M4UA kowDr28sYWr8qUfZSTYMlU5vx9zcCVdczRr0i3jbaWTI/zJoD6/fzLsdlHE9CeBR9Dnf dEIAddezopg7BoCnGtijJ8m98k5k5nA/IpB3M575xp8PXlnC+yXTwYWfMy8I/7Ke3/KG cObfFdiCJC+NPpExOQJ5m+eqM+jTLzdKwlVS8Y9vBmGpGV/Hh/k4m8Sa0Z2TEtIBzh2w sZWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=bVTXmmIE7IBPyxQrXnC0p71oDoaSop9Sc+enhFol2Bo=; b=nM4vak+Ytp8ikq6VmWvKOen+z8yxQ5gLVmRE7L244fjd2RYevk/8ZHjZkRAXa28TBM QoY0FKlWfqbpes+ipatXPRbAxc2+8rxhhl2x5/PerYnhgKh+bnR0W0UL7BuKw8WP3mJn x0rUamNzIF0SmOEGsiq2neZt7MpEuuwBviDqybSb212TXBn7VExdNmSQlX1xsukZEMoy NoEjvHkxNpCLpjNX+ab18j2PDBxv8VVv4CXxzJwDnHzJw4UxKHXR5ONw41ff3DjKuXp5 TAzCYLhzDuCj8Xu6hFRFYDyhw9JnIVhETq3sUATuaYsBQP+tXIEijnPboYwwx7F2bds/ 9CuA== X-Gm-Message-State: AOAM5308QvwaSTw0VU6fop9sB1kkXyXfAMhFhVDa/IYu4dd+P4/qeYSC cOKv0EVPAdbIaYs1kmSN12o= X-Google-Smtp-Source: ABdhPJz9p9KTTDNveDHP3SkVWKwd6ykXbiRr9Wu1NJs087UjkElIzqft81Kwft88Cb1HYeKfwSeycw== X-Received: by 2002:a17:902:bb0f:b0:149:d7c2:3e7f with SMTP id im15-20020a170902bb0f00b00149d7c23e7fmr5314532plb.109.1642091868514; Thu, 13 Jan 2022 08:37:48 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-e24f-43ff-fee6-449f.res6.spectrum.com. [2603:800c:1a02:1bae:e24f:43ff:fee6:449f]) by smtp.gmail.com with ESMTPSA id q9sm2696208pgv.71.2022.01.13.08.37.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Jan 2022 08:37:48 -0800 (PST) Sender: Tejun Heo Date: Thu, 13 Jan 2022 06:37:46 -1000 From: Tejun Heo To: Imran Khan Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/2] kernfs: use hashed mutex and spinlock in place of global ones. Message-ID: References: <20220113104259.1584491-1-imran.f.khan@oracle.com> <20220113104259.1584491-2-imran.f.khan@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220113104259.1584491-2-imran.f.khan@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Jan 13, 2022 at 09:42:58PM +1100, Imran Khan wrote: > +#ifdef CONFIG_SMP > +#define NR_KERNFS_LOCK_BITS (2 * (ilog2(NR_CPUS < 32 ? NR_CPUS : 32))) How did the 32 limit come to be? It'd be nice to have a comment explaining that this is something which affects scalability and brief rationale on the current number. > +static inline spinlock_t *open_node_lock_ptr(struct kernfs_node *kn) > +{ > + int index = hash_ptr(kn, NR_KERNFS_LOCK_BITS); > + > + return &kernfs_global_locks.open_node_locks[index].lock; > +} > + > +static inline struct mutex *open_file_mutex_ptr(struct kernfs_node *kn) > +{ > + int index = hash_ptr(kn, NR_KERNFS_LOCK_BITS); > + > + return &kernfs_global_locks.open_file_mutex[index].lock; > +} I wonder whether it'd be useful to provide some helpers so that users don't have to get the pointer for the lock and then lock it in separate steps. Would it make sense to provide something which locks and returns the pointer (or token)? Thanks. -- tejun