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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 4DA64C43444 for ; Thu, 17 Jan 2019 21:02:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 280EB20859 for ; Thu, 17 Jan 2019 21:02:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729387AbfAQVCr (ORCPT ); Thu, 17 Jan 2019 16:02:47 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48460 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729299AbfAQVCr (ORCPT ); Thu, 17 Jan 2019 16:02:47 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0B771C7A32; Thu, 17 Jan 2019 21:02:47 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F287F100194A; Thu, 17 Jan 2019 21:02:45 +0000 (UTC) From: Jeff Moyer To: Jens Axboe Cc: Roman Penyaev , linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-block@vger.kernel.org, linux-arch@vger.kernel.org, hch@lst.de, avi@scylladb.com, linux-block-owner@vger.kernel.org Subject: Re: [PATCH 05/15] Add io_uring IO interface References: <20190116175003.17880-1-axboe@kernel.dk> <20190116175003.17880-6-axboe@kernel.dk> <718b4d1fbe9f97592d6d7b76d7a4537d@suse.de> <02568485-cd10-182d-98e3-619077cf9bdc@kernel.dk> <3180aa85-68a6-0eb2-082b-f177344cefa9@kernel.dk> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Thu, 17 Jan 2019 16:02:45 -0500 In-Reply-To: <3180aa85-68a6-0eb2-082b-f177344cefa9@kernel.dk> (Jens Axboe's message of "Thu, 17 Jan 2019 13:53:10 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 17 Jan 2019 21:02:47 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Jens Axboe writes: >>>>>>> It seems that sq_entries, cq_entries are not limited at all. Can nasty >>>>>>> app consume a lot of kernel pages calling io_setup_uring() from a loop >>>>>>> passing random entries number? (or even better: decreasing entries >>>>>>> number, >>>>>>> in order to consume all pages orders with min number of loops). ... >>> One concern here is that, at least looking at my boxes, the default >>> setting for RLIMIT_MEMLOCK is really low. I'd hate for everyone to run >>> into issues using io_uring just because it seems to require root, >>> because the memlock limit is so low. >>> >>> That's much less of a concern with the fixed buffers, since it's a more >>> esoteric part of it. But everyone should be able to setup a few io_uring >>> queues and use them without having to worry about failing due to an >>> absurdly low RLIMIT_MEMLOCK. >>> >>> Comments? >> >> Yeah, the default is 64k here. We should probably up that. I'd say we >> either tackle the ridiculously low rlimits, or I guess we just go the >> aio route and add a sysctl. :-\ I'll see what's involved in the >> former. > > After giving it a bit of thought, let's go the rlimit route. It is cleaner, > and I don't want a sysctl knob for this either. 64k will enable anyone to > set up at least one decently sized ring. OK. Note that the MLOCK_LIMIT size has been dictated by gpg's requirements: commit f947ff8af30f75cb9cf0e966caf8f4809ad1b92e Author: Rik van Riel Date: Sun Aug 22 23:06:58 2004 -0700 [PATCH] increase per-user mlock limit default to 32k Since various gnupg users have indicated that gpg wants to mlock 32kB of memory, I created the patch below that increases the default mlock ulimit to 32kB. and then commit 0833422274ff00729a603b020fac297e69a03e40 Author: Kurt Garloff Date: Wed Oct 29 14:00:48 2008 -0700 mm: increase the default mlock limit from 32k to 64k ... However, newer gpg2 needs 64k in various circumstances and otherwise fails miserably, see bnc#329675. So all we need to do is modify gpg2 so that is requires more locked memory, and we're golden! ;-) -Jeff