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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 8B4E8C433DB for ; Mon, 22 Feb 2021 14:09:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E9CC964E57 for ; Mon, 22 Feb 2021 14:09:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9CC964E57 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 5DC388D0001; Mon, 22 Feb 2021 09:09:00 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 58C006B0078; Mon, 22 Feb 2021 09:09:00 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 455358D0001; Mon, 22 Feb 2021 09:09:00 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0191.hostedemail.com [216.40.44.191]) by kanga.kvack.org (Postfix) with ESMTP id 30D126B0075 for ; Mon, 22 Feb 2021 09:09:00 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id D4813759C for ; Mon, 22 Feb 2021 14:08:59 +0000 (UTC) X-FDA: 77846085198.30.A3E3409 Received: from outbound-smtp45.blacknight.com (outbound-smtp45.blacknight.com [46.22.136.57]) by imf10.hostedemail.com (Postfix) with ESMTP id 9A86140B8CEB for ; Mon, 22 Feb 2021 14:08:49 +0000 (UTC) Received: from mail.blacknight.com (pemlinmail01.blacknight.ie [81.17.254.10]) by outbound-smtp45.blacknight.com (Postfix) with ESMTPS id D435DFAB66 for ; Mon, 22 Feb 2021 14:08:50 +0000 (GMT) Received: (qmail 26699 invoked from network); 22 Feb 2021 14:08:50 -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 Feb 2021 14:08:50 -0000 Date: Mon, 22 Feb 2021 14:08:48 +0000 From: Mel Gorman To: Jesper Dangaard Brouer Cc: Chuck Lever , Mel Gorman , Linux NFS Mailing List , "linux-mm@kvack.org" , Jakub Kicinski , "netdev@vger.kernel.org" Subject: Re: alloc_pages_bulk() Message-ID: <20210222140848.GI3697@techsingularity.net> References: <20210210084155.GA3697@techsingularity.net> <20210210124103.56ed1e95@carbon> <20210210130705.GC3629@suse.de> <20210211091235.GC3697@techsingularity.net> <20210211132628.1fe4f10b@carbon> <20210215120056.GD3697@techsingularity.net> <20210215171038.42f62438@carbon> <20210222094256.GH3697@techsingularity.net> <20210222124246.690414a2@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20210222124246.690414a2@carbon> User-Agent: Mutt/1.10.1 (2018-07-13) X-Stat-Signature: p7xgbryw7y5x6ktga6ox7e55p6eymnqy X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 9A86140B8CEB Received-SPF: none (techsingularity.net>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=outbound-smtp45.blacknight.com; client-ip=46.22.136.57 X-HE-DKIM-Result: none/none X-HE-Tag: 1614002929-884307 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 Mon, Feb 22, 2021 at 12:42:46PM +0100, Jesper Dangaard Brouer wrote: > On Mon, 22 Feb 2021 09:42:56 +0000 > Mel Gorman wrote: > > > On Mon, Feb 15, 2021 at 05:10:38PM +0100, Jesper Dangaard Brouer wrote: > > > > > > On Mon, 15 Feb 2021 12:00:56 +0000 > > > Mel Gorman wrote: > > > > > > > On Thu, Feb 11, 2021 at 01:26:28PM +0100, Jesper Dangaard Brouer wrote: > > > [...] > > > > > > > > > I also suggest the API can return less pages than requested. Because I > > > > > want to to "exit"/return if it need to go into an expensive code path > > > > > (like buddy allocator or compaction). I'm assuming we have a flags to > > > > > give us this behavior (via gfp_flags or alloc_flags)? > > > > > > > > > > > > > The API returns the number of pages returned on a list so policies > > > > around how aggressive it should be allocating the requested number of > > > > pages could be adjusted without changing the API. Passing in policy > > > > requests via gfp_flags may be problematic as most (all?) bits are > > > > already used. > > > > > > Well, I was just thinking that I would use GFP_ATOMIC instead of > > > GFP_KERNEL to "communicate" that I don't want this call to take too > > > long (like sleeping). I'm not requesting any fancy policy :-) > > > > > > > The NFS use case requires opposite semantics > > -- it really needs those allocations to succeed > > https://lore.kernel.org/r/161340498400.7780.962495219428962117.stgit@klimt.1015granger.net. > > Sorry, but that is not how I understand the code. > > The code is doing exactly what I'm requesting. If the alloc_pages_bulk() > doesn't return expected number of pages, then check if others need to > run. The old code did schedule_timeout(msecs_to_jiffies(500)), while > Chuck's patch change this to ask for cond_resched(). Thus, it tries to > avoid blocking the CPU for too long (when allocating many pages). > > And the nfsd code seems to handle that the code can be interrupted (via > return -EINTR) via signal_pending(current). Thus, the nfsd code seems > to be able to handle if the page allocations failed. > I'm waiting to find out exactly what NFSD is currently doing as the code in 5.11 is not the same as what Chuck was coding against so I'm not 100% certain how it currently works. > > > I've asked what code it's based on as it's not 5.11 and I'll iron that > > out first. > > > > Then it might be clearer what the "can fail" semantics should look like. > > I think it would be best to have pairs of patches where the first patch > > adjusts the semantics of the bulk allocator and the second adds a user. > > That will limit the amount of code code carried in the implementation. > > When the initial users are in place then the implementation can be > > optimised as the optimisations will require significant refactoring and > > I not want to refactor multiple times. > > I guess, I should try to code-up the usage in page_pool. > > What is the latest patch for adding alloc_pages_bulk() ? > There isn't a usable latest version until I reconcile the nfsd caller. The only major change in the API right now is dropping order. It handles order-0 only. -- Mel Gorman SUSE Labs