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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 0A82AC433E2 for ; Fri, 19 Mar 2021 18:19:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D853C6198B for ; Fri, 19 Mar 2021 18:19:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230310AbhCSSSh (ORCPT ); Fri, 19 Mar 2021 14:18:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:49058 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230218AbhCSSSe (ORCPT ); Fri, 19 Mar 2021 14:18:34 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 082F6AC23; Fri, 19 Mar 2021 18:18:33 +0000 (UTC) To: Mel Gorman , Andrew Morton Cc: Chuck Lever , Jesper Dangaard Brouer , Christoph Hellwig , Alexander Duyck , Matthew Wilcox , LKML , Linux-Net , Linux-MM , Linux-NFS References: <20210312154331.32229-1-mgorman@techsingularity.net> <20210312154331.32229-4-mgorman@techsingularity.net> From: Vlastimil Babka Subject: Re: [PATCH 3/7] mm/page_alloc: Add a bulk page allocator Message-ID: <7c520bbb-efd7-7cad-95df-610000832a67@suse.cz> Date: Fri, 19 Mar 2021 19:18:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210312154331.32229-4-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/12/21 4:43 PM, Mel Gorman wrote: > This patch adds a new page allocator interface via alloc_pages_bulk, > and __alloc_pages_bulk_nodemask. A caller requests a number of pages > to be allocated and added to a list. They can be freed in bulk using > free_pages_bulk(). > > The API is not guaranteed to return the requested number of pages and > may fail if the preferred allocation zone has limited free memory, the > cpuset changes during the allocation or page debugging decides to fail > an allocation. It's up to the caller to request more pages in batch > if necessary. > > Note that this implementation is not very efficient and could be improved > but it would require refactoring. The intent is to make it available early > to determine what semantics are required by different callers. Once the > full semantics are nailed down, it can be refactored. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Although maybe premature, if it changes significantly due to the users' performance feedback, let's see :) Some nits below: ... > @@ -4963,6 +4978,107 @@ static inline bool prepare_alloc_pages(gfp_t gfp, unsigned int order, > return true; > } > > +/* > + * This is a batched version of the page allocator that attempts to > + * allocate nr_pages quickly from the preferred zone and add them to list. > + * > + * Returns the number of pages allocated. > + */ > +int __alloc_pages_bulk(gfp_t gfp, int preferred_nid, > + nodemask_t *nodemask, int nr_pages, > + struct list_head *alloc_list) > +{ > + struct page *page; > + unsigned long flags; > + struct zone *zone; > + struct zoneref *z; > + struct per_cpu_pages *pcp; > + struct list_head *pcp_list; > + struct alloc_context ac; > + gfp_t alloc_gfp; > + unsigned int alloc_flags; > + int allocated = 0; > + > + if (WARN_ON_ONCE(nr_pages <= 0)) > + return 0; > + > + if (nr_pages == 1) > + goto failed; > + > + /* May set ALLOC_NOFRAGMENT, fragmentation will return 1 page. */ > + if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, > + &alloc_gfp, &alloc_flags)) Unusual identation here. > + return 0; > + gfp = alloc_gfp; > + > + /* Find an allowed local zone that meets the high watermark. */ > + for_each_zone_zonelist_nodemask(zone, z, ac.zonelist, ac.highest_zoneidx, ac.nodemask) { > + unsigned long mark; > + > + if (cpusets_enabled() && (alloc_flags & ALLOC_CPUSET) && > + !__cpuset_zone_allowed(zone, gfp)) { > + continue; > + } > + > + if (nr_online_nodes > 1 && zone != ac.preferred_zoneref->zone && > + zone_to_nid(zone) != zone_to_nid(ac.preferred_zoneref->zone)) { > + goto failed; > + } > + > + mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages; > + if (zone_watermark_fast(zone, 0, mark, > + zonelist_zone_idx(ac.preferred_zoneref), > + alloc_flags, gfp)) { > + break; > + } > + } > + if (!zone) > + return 0; Why not also "goto failed;" here?