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From: Pavel Begunkov <[email protected]>
To: Dmitry Kadashev <[email protected]>
Cc: Jens Axboe <[email protected]>, Josef <[email protected]>,
	Norman Maurer <[email protected]>,
	io-uring <[email protected]>
Subject: Re: "Cannot allocate memory" on ring creation (not RLIMIT_MEMLOCK)
Date: Tue, 22 Dec 2020 04:07:49 +0000	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 22/12/2020 03:35, Pavel Begunkov wrote:
> On 21/12/2020 11:00, Dmitry Kadashev wrote:
> [snip]
>>> We do not share rings between processes. Our rings are accessible from different
>>> threads (under locks), but nothing fancy.
>>>
>>>> In other words, if you kill all your io_uring applications, does it
>>>> go back to normal?
>>>
>>> I'm pretty sure it does not, the only fix is to reboot the box. But I'll find an
>>> affected box and double check just in case.
> 
> I can't spot any misaccounting, but I wonder if it can be that your memory is
> getting fragmented enough to be unable make an allocation of 16 __contiguous__
> pages, i.e. sizeof(sqe) * 1024
> 
> That's how it's allocated internally:
> 
> static void *io_mem_alloc(size_t size)
> {
> 	gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_COMP |
> 				__GFP_NORETRY;
> 
> 	return (void *) __get_free_pages(gfp_flags, get_order(size));
> }
> 
> What about smaller rings? Can you check io_uring of what SQ size it can allocate?
> That can be a different program, e.g. modify a bit liburing/test/nop.

Even better to allocate N smaller rings, where N = 1024 / SQ_size

static int try_size(int sq_size)
{
	int ret = 0, i, n = 1024 / sq_size;
	static struct io_uring rings[128];

	for (i = 0; i < n; ++i) {
		if (io_uring_queue_init(sq_size, &rings[i], 0) < 0) {
			ret = -1;
			break;
		}
	}
	for (i -= 1; i >= 0; i--)
		io_uring_queue_exit(&rings[i]);
	return ret;
}

int main()
{
	int size;

	for (size = 1024; size >= 2; size /= 2) {
		if (!try_size(size)) {
			printf("max size %i\n", size);
			return 0;
		}
	}

	printf("can't allocate %i\n", size);
	return 0;
}


> Also, can you allocate it if you switch a user (preferably to non-root) after it
> happens?
> 
>>
>> So, I've just tried stopping everything that uses io-uring. No io_wq* processes
>> remained:
>>
>> $ ps ax | grep wq
>>     9 ?        I<     0:00 [mm_percpu_wq]
>>   243 ?        I<     0:00 [tpm_dev_wq]
>>   246 ?        I<     0:00 [devfreq_wq]
>> 27922 pts/4    S+     0:00 grep --colour=auto wq
>> $
>>
>> But not a single ring (with size 1024) can be created afterwards anyway.
>>
>> Apparently the problem netty hit and this one are different?
> 

-- 
Pavel Begunkov

  reply	other threads:[~2020-12-22  4:12 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-17  8:19 "Cannot allocate memory" on ring creation (not RLIMIT_MEMLOCK) Dmitry Kadashev
2020-12-17  8:26 ` Norman Maurer
2020-12-17  8:36   ` Dmitry Kadashev
2020-12-17  8:40     ` Dmitry Kadashev
2020-12-17 10:38       ` Josef
2020-12-17 11:10         ` Dmitry Kadashev
2020-12-17 13:43           ` Victor Stewart
2020-12-18  9:20             ` Dmitry Kadashev
2020-12-18 17:22               ` Jens Axboe
2020-12-18 15:26 ` Jens Axboe
2020-12-18 17:21   ` Josef
2020-12-18 17:23     ` Jens Axboe
2020-12-19  2:49       ` Josef
2020-12-19 16:13         ` Jens Axboe
2020-12-19 16:29           ` Jens Axboe
2020-12-19 17:11             ` Jens Axboe
2020-12-19 17:34               ` Norman Maurer
2020-12-19 17:38                 ` Jens Axboe
2020-12-19 20:51                   ` Josef
2020-12-19 21:54                     ` Jens Axboe
2020-12-19 23:13                       ` Jens Axboe
2020-12-19 23:42                         ` Josef
2020-12-19 23:42                         ` Pavel Begunkov
2020-12-20  0:25                           ` Jens Axboe
2020-12-20  0:55                             ` Pavel Begunkov
2020-12-21 10:35                               ` Dmitry Kadashev
2020-12-21 10:49                                 ` Dmitry Kadashev
2020-12-21 11:00                                 ` Dmitry Kadashev
2020-12-21 15:36                                   ` Pavel Begunkov
2020-12-22  3:35                                   ` Pavel Begunkov
2020-12-22  4:07                                     ` Pavel Begunkov [this message]
2020-12-22 11:04                                       ` Dmitry Kadashev
2020-12-22 11:06                                         ` Dmitry Kadashev
2020-12-22 13:13                                           ` Dmitry Kadashev
2020-12-22 16:33                                         ` Pavel Begunkov
2020-12-23  8:39                                           ` Dmitry Kadashev
2020-12-23  9:38                                             ` Dmitry Kadashev
2020-12-23 11:48                                               ` Dmitry Kadashev
2020-12-23 12:27                                                 ` Pavel Begunkov
2020-12-20  1:57                             ` Pavel Begunkov
2020-12-20  7:13                               ` Josef
2020-12-20 13:00                                 ` Pavel Begunkov
2020-12-20 14:19                                   ` Pavel Begunkov
2020-12-20 15:56                                     ` Josef
2020-12-20 15:58                                       ` Pavel Begunkov
2020-12-20 16:14                                   ` Jens Axboe
2020-12-20 16:59                                     ` Josef
2020-12-20 18:23                                       ` Josef
2020-12-20 18:41                                         ` Pavel Begunkov
2020-12-21  8:22                                           ` Josef
2020-12-21 15:30                                             ` Pavel Begunkov
2020-12-21 10:31               ` Dmitry Kadashev

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