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 X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F722C433E0 for ; Thu, 18 Jun 2020 17:57:23 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 27453207DD for ; Thu, 18 Jun 2020 17:57:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="0DoXDyQA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 27453207DD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8C7D38D004E; Thu, 18 Jun 2020 13:57:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 877C88D0018; Thu, 18 Jun 2020 13:57:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7B48A8D004E; Thu, 18 Jun 2020 13:57:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0051.hostedemail.com [216.40.44.51]) by kanga.kvack.org (Postfix) with ESMTP id 656E98D0018 for ; Thu, 18 Jun 2020 13:57:22 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D46F87E799 for ; Thu, 18 Jun 2020 17:57:21 +0000 (UTC) X-FDA: 76943089482.24.egg74_080026f26e12 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 9293F7E570 for ; Thu, 18 Jun 2020 17:57:21 +0000 (UTC) X-HE-Tag: egg74_080026f26e12 X-Filterd-Recvd-Size: 4256 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Thu, 18 Jun 2020 17:57:21 +0000 (UTC) Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 33C6620734; Thu, 18 Jun 2020 17:57:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592503040; bh=CpFWwPudG4VycBDt9MHz0afTFmGzYGQJeQyidiFbwYs=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=0DoXDyQAFSO+Ybw3F297GmKIj0ze8moUADsxYo/i5hyigIMYA14F8u0iRPJX1xyFV mnGcnaVHDXnobaD3k540slOUnK1d89LPoVmU/04UASXSNgXJilT/bmZ4vHjSH5psPj mXCZwTnOR2HEQl/UlYjIaXWleUuHqz8AqdbPBXMc= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 0309B35229B4; Thu, 18 Jun 2020 10:57:20 -0700 (PDT) Date: Thu, 18 Jun 2020 10:57:19 -0700 From: "Paul E. McKenney" To: Uladzislau Rezki Cc: Matthew Wilcox , LKML , linux-mm@kvack.org, Andrew Morton , "Theodore Y . Ts'o" , Joel Fernandes , RCU , Oleksiy Avramchenko Subject: Re: [PATCH v2 09/16] rcu/tree: Maintain separate array for vmalloc ptrs Message-ID: <20200618175719.GT2723@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200525214800.93072-1-urezki@gmail.com> <20200525214800.93072-10-urezki@gmail.com> <20200617234609.GA10087@paulmck-ThinkPad-P72> <20200618005214.GN8681@bombadil.infradead.org> <20200618031823.GQ2723@paulmck-ThinkPad-P72> <20200618173520.GC14613@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200618173520.GC14613@pc636> User-Agent: Mutt/1.9.4 (2018-02-28) X-Rspamd-Queue-Id: 9293F7E570 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 18, 2020 at 07:35:20PM +0200, Uladzislau Rezki wrote: > > > > > > I don't think that replacing direct function calls with indirect function > > > calls is a great suggestion with the current state of play around branch > > > prediction. > > > > > > I'd suggest: > > > > > > rcu_lock_acquire(&rcu_callback_map); > > > trace_rcu_invoke_kfree_bulk_callback(rcu_state.name, > > > bkvhead[i]->nr_records, bkvhead[i]->records); > > > if (i == 0) { > > > kfree_bulk(bkvhead[i]->nr_records, > > > bkvhead[i]->records); > > > } else { > > > for (j = 0; j < bkvhead[i]->nr_records; j++) { > > > vfree(bkvhead[i]->records[j]); > > > } > > > } > > > rcu_lock_release(&rcu_callback_map); > > > > > > But I'd also suggest a vfree_bulk be added. There are a few things > > > which would be better done in bulk as part of the vfree process > > > (we batch them up already, but i'm sure we could do better). > > > > I suspect that he would like to keep the tracing. > > > > It might be worth trying the branches, given that they would be constant > > and indexed by "i". The compiler might well remove the indirection. > > > > The compiler guys brag about doing so, which of course might or might > > not have any correlation to a given compiler actually doing so. :-/ > > > > Having a vfree_bulk() might well be useful, but I would feel more > > confidence in that if there were other callers of kfree_bulk(). > > > Hmm... I think replacing that with vfree_bulk() is a good idea though. In other words, get rid of kfree_bulk() in favor of vfree_bulk()? > > But again, either way, future work as far as this series is concerned. > > > What do you mean: is concerned? Apologies for the strange English. How about this? "This series is OK as is. Any comments above did not prevent me from taking these patches, but instead discuss possible future work." > We are planning to implement kfree_rcu() to be integrated directly into > SLAB: SLAB, SLUB, SLOB. So, there are plenty of future work :) And I am glad that this is still the goal. ;-) Thanx, Paul