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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 60378C2BA12 for ; Fri, 3 Apr 2020 18:16:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3614920737 for ; Fri, 3 Apr 2020 18:16:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ekPQvnbP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404564AbgDCSQ5 (ORCPT ); Fri, 3 Apr 2020 14:16:57 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:55446 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404179AbgDCSQ4 (ORCPT ); Fri, 3 Apr 2020 14:16:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Xqf9ldErwZipwjo+fl+eRLkju/QhT7uG+RO6CX07x18=; b=ekPQvnbPY7L+eQb/daLRoe0jc6 6U1Q8XG+26v6NeVbrGQTQP/8ME9htTQkw/MghIvemX1Yt/iCJap4R/s7vO6/UAOHurgtgLqtPc1f5 +6jaHJYcyPyrkvAcbHamlUa4BzkkBeyBjH3eqxRtC14p61ZEVZjnWZWbXqOW06tCxDPIpjAV2l/gN D346Q7MzPGJkpZqpX2l7zMFp1au3wa8tmBjRhBhBSnRfDhwU6ux+IyPbeLv2/t9zm0XHYnqOH8qRV xhw2VGKuTdqjGi4Xsg3cOlL7FfVKejr0TzkUWdLZY+fQMs2V+YXnI6UqK8YHXSzeXa2FTT9joH8KS ok/l668w==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jKQsB-0006kJ-Af; Fri, 03 Apr 2020 18:16:55 +0000 Date: Fri, 3 Apr 2020 11:16:55 -0700 From: Matthew Wilcox To: "Uladzislau Rezki (Sony)" Cc: LKML , "Paul E . McKenney" , Joel Fernandes , RCU , linux-mm@kvack.org, Andrew Morton , Steven Rostedt , Oleksiy Avramchenko Subject: Re: [PATCH 1/1] rcu/tree: add emergency pool for headless case Message-ID: <20200403181655.GR21484@bombadil.infradead.org> References: <20200403173051.4081-1-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200403173051.4081-1-urezki@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 03, 2020 at 07:30:51PM +0200, Uladzislau Rezki (Sony) wrote: > @@ -2877,6 +2885,12 @@ struct kfree_rcu_cpu { > bool initialized; > // Number of objects for which GP not started > int count; > + > + /* > + * Reserved emergency pool for headless variant. > + */ > + int nr_emergency; > + void **emergency; This is a pretty expensive way to maintain an emergency pool. Try something like this ... struct emergency_pool_object { union { struct whatever foo; struct { int remaining; void *next; }; }; }; struct kfree_rcu_cpu { ... struct emergency_pool_object *epo; }; struct whatever *get_emergency_object(struct kfree_rcu_cpu *krc) { struct emergency_pool_object *epo = krc->epo; if (epo) krc->epo = epo->next; return &epo->foo; } void alloc_emergency_objects(struct kfree_rcu_cpu *krc, int n) { int i = 0; if (krc->epo) i = krc->epo->remaining; while (++i < n) { struct emergency_pool_object *epo = kmalloc(sizeof(epo), GFP); epo->remaining = i; epo->next = krc->epo; krc->epo = epo; } }