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 14:17:05 -0700 Message-ID: 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> 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 2:02 PM, Jeff Moyer wrote: > 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! ;-) Haha, that's some nice digging there! Yes, we could bump it, but with the default, we can get a 512 sized ring per user, that's 13 pages (rounded up). Probably good enough to get things off the ground? -- 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-f195.google.com ([209.85.166.195]:54838 "EHLO mail-it1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728436AbfAQVRJ (ORCPT ); Thu, 17 Jan 2019 16:17:09 -0500 Received: by mail-it1-f195.google.com with SMTP id i145so3733192ita.4 for ; Thu, 17 Jan 2019 13:17:08 -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> <3180aa85-68a6-0eb2-082b-f177344cefa9@kernel.dk> From: Jens Axboe Message-ID: Date: Thu, 17 Jan 2019 14:17:05 -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: <20190117211705.NaQe7TDuY2XD3kq8Jwx5-brMwM9_pzeuG2fUYeoWuKA@z> On 1/17/19 2:02 PM, Jeff Moyer wrote: > 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! ;-) Haha, that's some nice digging there! Yes, we could bump it, but with the default, we can get a 512 sized ring per user, that's 13 pages (rounded up). Probably good enough to get things off the ground? -- Jens Axboe