From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH 05/15] Add io_uring IO interface Date: Thu, 17 Jan 2019 13:53:10 -0700 Message-ID: <3180aa85-68a6-0eb2-082b-f177344cefa9@kernel.dk> References: <20190116175003.17880-1-axboe@kernel.dk> <20190116175003.17880-6-axboe@kernel.dk> <718b4d1fbe9f97592d6d7b76d7a4537d@suse.de> <02568485-cd10-182d-98e3-619077cf9bdc@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: owner-linux-aio@kvack.org To: Jeff Moyer 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 List-Id: linux-arch.vger.kernel.org On 1/17/19 1:50 PM, Jeff Moyer wrote: > 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. 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. -- Jens Axboe -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: aart@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it1-f194.google.com ([209.85.166.194]:38888 "EHLO mail-it1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727300AbfAQUxO (ORCPT ); Thu, 17 Jan 2019 15:53:14 -0500 Received: by mail-it1-f194.google.com with SMTP id h65so3039438ith.3 for ; Thu, 17 Jan 2019 12:53:13 -0800 (PST) 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> From: Jens Axboe Message-ID: <3180aa85-68a6-0eb2-082b-f177344cefa9@kernel.dk> Date: Thu, 17 Jan 2019 13:53:10 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Jeff Moyer 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 Message-ID: <20190117205310.EQFifT3JxlFQHlDcXd7nLy1VYj5FW2nPMgpV8bPACxA@z> On 1/17/19 1:50 PM, Jeff Moyer wrote: > 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. 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. -- Jens Axboe