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From: Jens Axboe <axboe@kernel.dk>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Roman Penyaev <rpenyaev@suse.de>,
	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
Date: Thu, 17 Jan 2019 14:17:05 -0700
Message-ID: <c86dbb69-1937-5a0d-11ff-98d933f6581a@kernel.dk> (raw)
In-Reply-To: <x49y37j6lqi.fsf@segfault.boston.devel.redhat.com>

On 1/17/19 2:02 PM, Jeff Moyer wrote:
> Jens Axboe <axboe@kernel.dk> 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 <riel@redhat.com>
> 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 <garloff@suse.de>
> 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


  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 17:49 [PATCHSET v5] " Jens Axboe
2019-01-16 17:49 ` [PATCH 01/15] fs: add an iopoll method to struct file_operations Jens Axboe
2019-01-16 17:49 ` [PATCH 02/15] block: wire up block device iopoll method Jens Axboe
2019-01-16 17:49 ` [PATCH 03/15] block: add bio_set_polled() helper Jens Axboe
2019-01-16 17:49 ` [PATCH 04/15] iomap: wire up the iopoll method Jens Axboe
2019-01-16 17:49 ` [PATCH 05/15] Add io_uring IO interface Jens Axboe
2019-01-17 12:02   ` Roman Penyaev
2019-01-17 13:54     ` Jens Axboe
2019-01-17 14:34       ` Roman Penyaev
2019-01-17 14:54         ` Jens Axboe
2019-01-17 15:19           ` Roman Penyaev
2019-01-17 12:48   ` Roman Penyaev
2019-01-17 14:01     ` Jens Axboe
2019-01-17 20:03       ` Jeff Moyer
2019-01-17 20:09         ` Jens Axboe
2019-01-17 20:14           ` Jens Axboe
2019-01-17 20:50             ` Jeff Moyer
2019-01-17 20:53               ` Jens Axboe
2019-01-17 21:02                 ` Jeff Moyer
2019-01-17 21:17                   ` Jens Axboe [this message]
2019-01-17 21:21                     ` Jeff Moyer
2019-01-17 21:27                       ` Jens Axboe
2019-01-18  8:23               ` Roman Penyaev
2019-01-16 17:49 ` [PATCH 06/15] io_uring: add fsync support Jens Axboe
2019-01-16 17:49 ` [PATCH 07/15] io_uring: support for IO polling Jens Axboe
2019-01-16 17:49 ` [PATCH 08/15] fs: add fget_many() and fput_many() Jens Axboe
2019-01-16 17:49 ` [PATCH 09/15] io_uring: use fget/fput_many() for file references Jens Axboe
2019-01-16 17:49 ` [PATCH 10/15] io_uring: batch io_kiocb allocation Jens Axboe
2019-01-16 17:49 ` [PATCH 11/15] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2019-01-16 17:50 ` [PATCH 12/15] io_uring: add support for pre-mapped user IO buffers Jens Axboe
2019-01-16 20:53   ` Dave Chinner
2019-01-16 21:20     ` Jens Axboe
2019-01-16 22:09       ` Dave Chinner
2019-01-16 22:21         ` Jens Axboe
2019-01-16 23:09           ` Dave Chinner
2019-01-16 23:17             ` Jens Axboe
2019-01-16 22:13       ` Jens Axboe
2019-01-16 17:50 ` [PATCH 13/15] io_uring: add submission polling Jens Axboe
2019-01-16 17:50 ` [PATCH 14/15] io_uring: add file registration Jens Axboe
2019-01-16 17:50 ` [PATCH 15/15] io_uring: add io_uring_event cache hit information Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2019-01-10  2:43 [PATCHSET v2] io_uring IO interface Jens Axboe
2019-01-10  2:43 ` [PATCH 05/15] Add " Jens Axboe
2019-01-11 18:19   ` Martin K. Petersen
2019-01-11 18:34     ` Jens Axboe
2019-01-13 16:22       ` Jens Axboe
2019-01-15 17:31         ` Martin K. Petersen

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