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 34D25C433FE for ; Thu, 13 Jan 2022 16:42:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236822AbiAMQmH (ORCPT ); Thu, 13 Jan 2022 11:42:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38498 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236816AbiAMQmE (ORCPT ); Thu, 13 Jan 2022 11:42:04 -0500 Received: from mail-pl1-x633.google.com (mail-pl1-x633.google.com [IPv6:2607:f8b0:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E52B1C061574 for ; Thu, 13 Jan 2022 08:42:03 -0800 (PST) Received: by mail-pl1-x633.google.com with SMTP id f13so359667plg.0 for ; Thu, 13 Jan 2022 08:42:03 -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=0RghS5in1nYPx/uEnl/bNk9uJrbAUCko5BnNI6t0d7A=; b=bd3akMxtoY9qvnWlzDOgFdInNxVVmO3jCTQLlz+Cnj32CwJ/Sd+XulfUMvK2MYIbDK 7PCplGYtZY46Gasvui4ntsgcBBZkej6h3k9GHvHaa7sE6jGx59JWCDaGVT7CA3KpzJU7 yHl93n7/RD4QoBPDhY3u3w1pAsrcjwfomlVc+eSMtHdZLUceGAp85X6gloMAtk+GooNA MG/XziYC8b8Ive3teUvzEGvWddQVX4HuwoT+Fqh5EfunOv/Gie4zAeeC2Dro78ZnzhRd G3MQqVYcoqWZR5I85Q9TOhGFHxWFJt0/U66P/53E3RtF79RQiakO+kPK4SSPH8PRNIls m1bA== 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=0RghS5in1nYPx/uEnl/bNk9uJrbAUCko5BnNI6t0d7A=; b=tFSI+HMzxL145R9ePgP+4yNj17rrp9XSmczipWMYJ5k6q7LSzAogBzvRQMtXYOL7aU DEXAeDsDl0BLEBz/0NYY8e9Q/EnhhnmX44igmZbCCyf5WWAb7el5FB+bEgOWREQBPIiG QCiI+kN99F1ll2nRl4ZBaAcchvoWxR+EKLw8fEZ4YnoxJy3qG2oG1DRwOmG1CA+8GuBX iZXCwmOm3SszlTVVRrUgr2Cj3OxrOIWp/K/fj5yAseGC1CTRIZR2K/j854KMlBSeNHDM RDZ+jw5uTmjR9Yg24bF5CD1dB0Dz8UckVPED7hdYoRENe3oifI7FZUPoB8oKtyJbAHZM dWdQ== X-Gm-Message-State: AOAM530kD17YU4sfceuzSm+aS7Tak1vN/hhAcmR4HCs/KWTcnvprvfqs KzdTL+0HrGfXsSuf/+P56s3XOuiEj8YRhQ== X-Google-Smtp-Source: ABdhPJxLuSieBetOIm6dcQtHfslT5H9JQcUa7G0tZf3pMJQrfLp/pmtvJyCqg1YC06fJYRbB8wg8ng== X-Received: by 2002:a17:90a:b281:: with SMTP id c1mr6047150pjr.221.1642092123302; Thu, 13 Jan 2022 08:42:03 -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 a14sm3660044pfv.18.2022.01.13.08.42.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Jan 2022 08:42:02 -0800 (PST) Sender: Tejun Heo Date: Thu, 13 Jan 2022 06:42:01 -1000 From: Tejun Heo To: Imran Khan Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] kernfs: Reduce contention around global per-fs kernfs_rwsem. Message-ID: References: <20220113104259.1584491-1-imran.f.khan@oracle.com> <20220113104259.1584491-3-imran.f.khan@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220113104259.1584491-3-imran.f.khan@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Jan 13, 2022 at 09:42:59PM +1100, Imran Khan wrote: > @@ -748,11 +749,14 @@ int kernfs_add_one(struct kernfs_node *kn) > goto out_unlock; > > /* Update timestamps on the parent */ > + rwsem = iattr_rwsem_ptr(parent); > + down_write(rwsem); > ps_iattr = parent->iattr; > if (ps_iattr) { > ktime_get_real_ts64(&ps_iattr->ia_ctime); > ps_iattr->ia_mtime = ps_iattr->ia_ctime; > } > + up_write(rwsem); > > up_write(&root->kernfs_rwsem); Hmmm, so the additions / removals are still fs-global lock protected. Would it be possible to synchronize them through hashed locks too? We can provide double locking helpers - look up locks for both parent and child and if different lock in the defined order (parent first most likely) and record what happened in a token so that it can be undone later. Without going through the code carefully, I don't remember whether there's something which depends on global locking but I'm sure we can fix them too. It'd be really nice if we can make all operations similarly scalable cuz with heavy stacking addition/removals can get pretty hot too. Thanks. -- tejun