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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 B2F0BC433DB for ; Mon, 22 Mar 2021 08:30:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 177DB61967 for ; Mon, 22 Mar 2021 08:30:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 177DB61967 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=techsingularity.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C60CF6B0036; Mon, 22 Mar 2021 04:11:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C11196B006C; Mon, 22 Mar 2021 04:11:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A9F676B0070; Mon, 22 Mar 2021 04:11:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0067.hostedemail.com [216.40.44.67]) by kanga.kvack.org (Postfix) with ESMTP id 8C1CE6B0036 for ; Mon, 22 Mar 2021 04:11:53 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id DE04E1802799D for ; Mon, 22 Mar 2021 08:30:43 +0000 (UTC) X-FDA: 77946839166.10.5E978A1 Received: from outbound-smtp57.blacknight.com (outbound-smtp57.blacknight.com [46.22.136.241]) by imf03.hostedemail.com (Postfix) with ESMTP id E19B5C0007CB for ; Mon, 22 Mar 2021 08:30:42 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail04.blacknight.ie [81.17.254.17]) by outbound-smtp57.blacknight.com (Postfix) with ESMTPS id 671BDFBB88 for ; Mon, 22 Mar 2021 08:30:41 +0000 (GMT) Received: (qmail 12857 invoked from network); 22 Mar 2021 08:30:41 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 22 Mar 2021 08:30:41 -0000 Date: Mon, 22 Mar 2021 08:30:39 +0000 From: Mel Gorman To: Vlastimil Babka Cc: Andrew Morton , Chuck Lever , Jesper Dangaard Brouer , Christoph Hellwig , Alexander Duyck , Matthew Wilcox , LKML , Linux-Net , Linux-MM , Linux-NFS Subject: Re: [PATCH 3/7] mm/page_alloc: Add a bulk page allocator Message-ID: <20210322083039.GD3697@techsingularity.net> References: <20210312154331.32229-1-mgorman@techsingularity.net> <20210312154331.32229-4-mgorman@techsingularity.net> <7c520bbb-efd7-7cad-95df-610000832a67@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <7c520bbb-efd7-7cad-95df-610000832a67@suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Stat-Signature: rqwfaichhwutdoeepagan1uqhcbnfdqu X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: E19B5C0007CB Received-SPF: none (techsingularity.net>: No applicable sender policy available) receiver=imf03; identity=mailfrom; envelope-from=""; helo=outbound-smtp57.blacknight.com; client-ip=46.22.136.241 X-HE-DKIM-Result: none/none X-HE-Tag: 1616401842-613283 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, Mar 19, 2021 at 07:18:32PM +0100, Vlastimil Babka wrote: > 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 :) > Indeed. The next version will have no users so that Jesper and Chuck can check if an array-based or LRU based version is better. There were also bugs such as broken accounting of stats that had to be fixed which increases overhead. > 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. > Fixed > > + 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? Good question. When first written, it was because the zone search for the normal allocator was almost certainly going to fail to find a zone and it was expected that callers would prefer to fail fast over blocking. Now we know that sunrpc can sleep on a failing allocation and it would be better to enter the single page allocator and reclaim pages instead of "sleep and hope for the best". -- Mel Gorman SUSE Labs