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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 339DBC433F5 for ; Wed, 24 Nov 2021 14:38:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349456AbhKXOlN (ORCPT ); Wed, 24 Nov 2021 09:41:13 -0500 Received: from smtp-out2.suse.de ([195.135.220.29]:53938 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345299AbhKXOlE (ORCPT ); Wed, 24 Nov 2021 09:41:04 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 188741FD2F; Wed, 24 Nov 2021 14:37:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1637764673; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=g89M6e4bZVmCAGamFZFhx+PTBdJYL4rU4pHyE6Arzw4=; b=EyZrDNrfpR7D5fH5oI12w5LWSmiNa4aXC3QlPr7YAZyqG3LiF9AbI/17RNZ9LptDFlpdQT AeibRGRQWbMy5hMySB6lMYUNWVKB6tUK+n+6fj87rZQtM0EMZaINBpn9Y3XuJIPmV5ipjg rawBAvdahJ9WTtg2kyAOVc38Yob+r44= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1637764673; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=g89M6e4bZVmCAGamFZFhx+PTBdJYL4rU4pHyE6Arzw4=; b=kbd0ArkzFfW6iG8MSbD41gl/ohcBQzmXdtXUYxxIgWwqASW/a40zXPP3GJWa+EXdwrDk1Y iur/avAO8UavRwCg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id E08D113F19; Wed, 24 Nov 2021 14:37:52 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id A4LcNUBOnmEjagAAMHmgww (envelope-from ); Wed, 24 Nov 2021 14:37:52 +0000 Message-ID: Date: Wed, 24 Nov 2021 15:37:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB Content-Language: en-US To: David Hildenbrand , Jason Gunthorpe Cc: Jens Axboe , Andrew Dona-Couch , Andrew Morton , Drew DeVault , Ammar Faizi , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, io_uring Mailing List , Pavel Begunkov , linux-mm@kvack.org References: <8f219a64-a39f-45f0-a7ad-708a33888a3b@www.fastmail.com> <333cb52b-5b02-648e-af7a-090e23261801@redhat.com> <5f998bb7-7b5d-9253-2337-b1d9ea59c796@redhat.com> <20211123132523.GA5112@ziepe.ca> <10ccf01b-f13a-d626-beba-cbee70770cf1@redhat.com> <20211123140709.GB5112@ziepe.ca> <20211123170056.GC5112@ziepe.ca> <20211123235953.GF5112@ziepe.ca> <2adca04f-92e1-5f99-6094-5fac66a22a77@redhat.com> From: Vlastimil Babka In-Reply-To: <2adca04f-92e1-5f99-6094-5fac66a22a77@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 11/24/21 09:57, David Hildenbrand wrote: > On 24.11.21 00:59, Jason Gunthorpe wrote: >>> Similarly for io-uring we could be migrating pages to be pinned so that >>> the end up consolidated close together, and prevent pathologic >>> situations like in David's reproducer. >> >> It is an interesting idea to have GUP do some kind of THP preserving >> migration. > > > Unfortunately it will only be a band aid AFAIU. I can rewrite my > reproducer fairly easily to pin the whole 2M range first, pin a second > time only a single page, and then unpin the 2M range, resulting in the > very same way to block THP. (I can block some THP less because I always > need the possibility to memlock 2M first, though). Hm I see, then we could also condsider making it possible to migrate the pinned pages - of course io-uring would have to be cooperative here, similarly to anything that supports PageMovable. Mlocked pages can also be migrated (I think there's some sysctl to prevent that, if the guarantee of not even a minor pagefault is considered more important).