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 B4AC3C43387 for ; Thu, 17 Jan 2019 20:50:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CDDD20868 for ; Thu, 17 Jan 2019 20:50:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727883AbfAQUuu (ORCPT ); Thu, 17 Jan 2019 15:50:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58564 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726905AbfAQUuu (ORCPT ); Thu, 17 Jan 2019 15:50:50 -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 7BD63C051663; Thu, 17 Jan 2019 20:50:49 +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 4AB3E1001F59; Thu, 17 Jan 2019 20:50:48 +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> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Thu, 17 Jan 2019 15:50:47 -0500 In-Reply-To: <02568485-cd10-182d-98e3-619077cf9bdc@kernel.dk> (Jens Axboe's message of "Thu, 17 Jan 2019 13:14:09 -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 [10.5.110.31]); Thu, 17 Jan 2019 20:50:49 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Jens Axboe writes: > On 1/17/19 1:09 PM, Jens Axboe wrote: >> On 1/17/19 1:03 PM, Jeff Moyer wrote: >>> Jens Axboe writes: >>> >>>> On 1/17/19 5:48 AM, Roman Penyaev wrote: >>>>> On 2019-01-16 18:49, Jens Axboe wrote: >>>>> >>>>> [...] >>>>> >>>>>> +static int io_allocate_scq_urings(struct io_ring_ctx *ctx, >>>>>> + struct io_uring_params *p) >>>>>> +{ >>>>>> + struct io_sq_ring *sq_ring; >>>>>> + struct io_cq_ring *cq_ring; >>>>>> + size_t size; >>>>>> + int ret; >>>>>> + >>>>>> + sq_ring = io_mem_alloc(struct_size(sq_ring, array, p->sq_entries)); >>>>> >>>>> 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). >>>> >>>> Yes, that's an oversight, we should have a limit in place. I'll add that. >>> >>> Can we charge the ring memory to the RLIMIT_MEMLOCK as well? I'd prefer >>> not to repeat the mistake of fs.aio-max-nr. >> >> Sure, we can do that. With the ring limited in size (it's now 4k entries >> at most), the amount of memory gobbled up by that is much smaller than >> the fixed buffers. A max sized ring is about 256k of memory. Per io_uring. Nothing prevents a user from calling io_uring_setup in a loop and continuing to gobble up memory. > 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. -Jeff