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From: Jeff Moyer <jmoyer@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
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 15:50:47 -0500
Message-ID: <x4936pr80uw.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <02568485-cd10-182d-98e3-619077cf9bdc@kernel.dk>

Jens Axboe <axboe@kernel.dk> writes:

> On 1/17/19 1:09 PM, Jens Axboe wrote:
>> On 1/17/19 1:03 PM, Jeff Moyer wrote:
>>> Jens Axboe <axboe@kernel.dk> 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

  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 [this message]
2019-01-17 20:53               ` Jens Axboe
2019-01-17 21:02                 ` Jeff Moyer
2019-01-17 21:17                   ` Jens Axboe
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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