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 49B09C43331 for ; Fri, 3 Apr 2020 18:17:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 06C3A206F5 for ; Fri, 3 Apr 2020 18:17:06 +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" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 06C3A206F5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8D5968E0008; Fri, 3 Apr 2020 14:17:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 885888E0007; Fri, 3 Apr 2020 14:17:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 77D8A8E0008; Fri, 3 Apr 2020 14:17:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0208.hostedemail.com [216.40.44.208]) by kanga.kvack.org (Postfix) with ESMTP id 5B4E28E0007 for ; Fri, 3 Apr 2020 14:17:06 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 1613B8248D7C for ; Fri, 3 Apr 2020 18:17:06 +0000 (UTC) X-FDA: 76667350452.21.ring38_77b0bc1ef1654 X-HE-Tag: ring38_77b0bc1ef1654 X-Filterd-Recvd-Size: 2922 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Apr 2020 18:17:02 +0000 (UTC) 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> 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 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; } }