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 17B6CC6FD1C for ; Fri, 24 Mar 2023 00:19:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229945AbjCXATL (ORCPT ); Thu, 23 Mar 2023 20:19:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56614 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229589AbjCXATK (ORCPT ); Thu, 23 Mar 2023 20:19:10 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC361CC05; Thu, 23 Mar 2023 17:19:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 55E956280C; Fri, 24 Mar 2023 00:19:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7EDBC433EF; Fri, 24 Mar 2023 00:19:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679617148; bh=IT1NxcXw2pAVasDPEQHbwE+mpHcOER7ahsHXYZ2RRJU=; h=Date:From:To:Cc:Subject:Reply-To:From; b=YNUC1KV7PPaLp93YVhVlnR9dfxSOQ0WEOoKPTsw1KgEkzFS52OxMD9wiiEqjruYFA IAsi6DHiQe6BGt6xJbz+dnKKpyz7m04AgbC1nDXhW56uYkb5nTUyJf/daRx0Cgd2Q5 XEJPhWnEb1bY+BqDDOr3fH3jxNTWPai2sh68ZmZkkvLnXWX2MW64vTbnxxE509Nisw 513/q2+HMmw9uiG+3MrHwLza6XzvEc9Iqe8CLrdDIivd5b0xDL5Z0Nzdl5pn5zOg3m BFT80JWN/SUs493CzakatMdKabQboRPGTDgyfnK6Mgz2dqsfrkCJCFVnuZcuVzXY3E Ke5RfvWuJn0ag== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 5626F1540379; Thu, 23 Mar 2023 17:19:08 -0700 (PDT) Date: Thu, 23 Mar 2023 17:19:08 -0700 From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, hch@lst.de Subject: [PATCH RFC rcu 0/19] Further shrink srcu_struct to promote cache locality Message-ID: <3db82572-f156-4a5d-b711-841aa28bd996@paulmck-laptop> Reply-To: paulmck@kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Hello! This RFC series shrinks the srcu_struct structure to the bare minimum required to support SRCU readers, relegating the remaining fields to a new srcu_usage structure. Statically allocated srcu_struct structures created by DEFINE_SRCU() and DEFINE_STATIC_SRCU() have statically allocated srcu_usage structures, but those required for dynamically allocated srcu_struct structures that are initialized using init_srcu_struct() are dynamically allocated. The results is a reduction in the size of an srcu_struct structure from a couple hundred bytes to just 24 bytes on x86_64 systems. This can be helpful when SRCU readers are used in a fastpath for which the srcu_struct structure must be embedded in another structure, and especially where that fastpath also needs to access fields both before and after the srcu_struct structure. This series takes baby steps, in part because breaking SRCU means that you get absolutely no console output. Yes, I did learn this the hard way. Why do you ask? ;-) Here are those baby steps: 1. Add whitespace to __SRCU_STRUCT_INIT() & __DEFINE_SRCU(). 2. Use static init for statically allocated in-module srcu_struct. 3. Begin offloading srcu_struct fields to srcu_update. Note that this affects notifiers, which open-code static allocation of an srcu_struct structure. (And no, I still do not see a way to abstract this, sorry!) 4. Move ->level from srcu_struct to srcu_usage. 5. Move ->srcu_size_state from srcu_struct to srcu_usage. 6. Move ->srcu_cb_mutex from srcu_struct to srcu_usage. 7. Move ->lock initialization after srcu_usage allocation. 8. Move ->lock from srcu_struct to srcu_usage. 9. Move ->srcu_gp_mutex from srcu_struct to srcu_usage. 10. Move grace-period fields from srcu_struct to srcu_usage. 11. Move heuristics fields from srcu_struct to srcu_usage. 12. Move ->sda_is_static from srcu_struct to srcu_usage. 13. Move srcu_barrier() fields from srcu_struct to srcu_usage. 14. Move work-scheduling fields from srcu_struct to srcu_usage. 15. Fix long lines in srcu_get_delay(). 16. Fix long lines in cleanup_srcu_struct(). 17. Fix long lines in srcu_gp_end(). 18. Fix long lines in srcu_funnel_gp_start(). 19. Remove extraneous parentheses from srcu_read_lock() etc. Thanx, Paul ------------------------------------------------------------------------ b/include/linux/notifier.h | 5 b/include/linux/srcu.h | 8 b/include/linux/srcutiny.h | 6 b/include/linux/srcutree.h | 28 +- b/kernel/rcu/rcu.h | 6 b/kernel/rcu/srcutree.c | 19 + include/linux/srcutree.h | 123 ++++++----- kernel/rcu/srcutree.c | 488 +++++++++++++++++++++++---------------------- 8 files changed, 368 insertions(+), 315 deletions(-)