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From: Jens Axboe <[email protected]>
To: Matthew Wilcox <[email protected]>
Cc: Kanchan Joshi <[email protected]>,
	[email protected], [email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	Selvakumar S <[email protected]>,
	Nitesh Shetty <[email protected]>,
	Javier Gonzalez <[email protected]>
Subject: Re: [PATCH v3 4/4] io_uring: add support for zone-append
Date: Tue, 7 Jul 2020 16:37:55 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 7/7/20 4:18 PM, Matthew Wilcox wrote:
> On Tue, Jul 07, 2020 at 02:40:06PM -0600, Jens Axboe wrote:
>>>> so we have another 24 bytes before io_kiocb takes up another cacheline.
>>>> If that's a serious problem, I have an idea about how to shrink struct
>>>> kiocb by 8 bytes so struct io_rw would have space to store another
>>>> pointer.
>>> Yes, io_kiocb has room. Cache-locality wise whether that is fine or
>>> it must be placed within io_rw - I'll come to know once I get to
>>> implement this. Please share the idea you have, it can come handy.
>>
>> Except it doesn't, I'm not interested in adding per-request type fields
>> to the generic part of it. Before we know it, we'll blow past the next
>> cacheline.
>>
>> If we can find space in the kiocb, that'd be much better. Note that once
>> the async buffered bits go in for 5.9, then there's no longer a 4-byte
>> hole in struct kiocb.
> 
> Well, poot, I was planning on using that.  OK, how about this:

Figured you might have had your sights set on that one, which is why I
wanted to bring it up upfront :-)

> +#define IOCB_NO_CMPL		(15 << 28)
> 
>  struct kiocb {
> [...]
> -	void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
> +	loff_t __user *ki_uposp;
> -	int			ki_flags;
> +	unsigned int		ki_flags;
> 
> +typedef void ki_cmpl(struct kiocb *, long ret, long ret2);
> +static ki_cmpl * const ki_cmpls[15];
> 
> +void ki_complete(struct kiocb *iocb, long ret, long ret2)
> +{
> +	unsigned int id = iocb->ki_flags >> 28;
> +
> +	if (id < 15)
> +		ki_cmpls[id](iocb, ret, ret2);
> +}
> 
> +int kiocb_cmpl_register(void (*cb)(struct kiocb *, long, long))
> +{
> +	for (i = 0; i < 15; i++) {
> +		if (ki_cmpls[id])
> +			continue;
> +		ki_cmpls[id] = cb;
> +		return id;
> +	}
> +	WARN();
> +	return -1;
> +}

That could work, we don't really have a lot of different completion
types in the kernel.

-- 
Jens Axboe


  reply	other threads:[~2020-07-07 22:38 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200705185204epcas5p3adeb4fc3473c5fc0472a7396783c5267@epcas5p3.samsung.com>
2020-07-05 18:47 ` [PATCH v3 0/4] zone-append support in io-uring and aio Kanchan Joshi
     [not found]   ` <CGME20200705185211epcas5p4059d05d2fcedb91829300a7a7d03fda3@epcas5p4.samsung.com>
2020-07-05 18:47     ` [PATCH v3 1/4] fs: introduce FMODE_ZONE_APPEND and IOCB_ZONE_APPEND Kanchan Joshi
     [not found]   ` <CGME20200705185217epcas5p1cc12d4b892f057a1fe06d73a00869daa@epcas5p1.samsung.com>
2020-07-05 18:47     ` [PATCH v3 2/4] block: add zone append handling for direct I/O path Kanchan Joshi
     [not found]   ` <CGME20200705185221epcas5p28b6d060df829b751109265222285da0e@epcas5p2.samsung.com>
2020-07-05 18:47     ` [PATCH v3 3/4] block: enable zone-append for iov_iter of bvec type Kanchan Joshi
     [not found]   ` <CGME20200705185227epcas5p16fba3cb92561794b960184c89fdf2bb7@epcas5p1.samsung.com>
2020-07-05 18:47     ` [PATCH v3 4/4] io_uring: add support for zone-append Kanchan Joshi
2020-07-05 21:00       ` Jens Axboe
2020-07-05 21:09         ` Matthew Wilcox
2020-07-05 21:12           ` Jens Axboe
2020-07-06 14:10             ` Matthew Wilcox
2020-07-06 14:27               ` Jens Axboe
2020-07-06 14:32                 ` Matthew Wilcox
2020-07-06 14:33                   ` Jens Axboe
2020-07-07 15:11                   ` Kanchan Joshi
2020-07-07 15:52                     ` Matthew Wilcox
2020-07-07 16:00                       ` Christoph Hellwig
2020-07-07 20:23                       ` Kanchan Joshi
2020-07-07 20:40                         ` Jens Axboe
2020-07-07 22:18                           ` Matthew Wilcox
2020-07-07 22:37                             ` Jens Axboe [this message]
2020-07-08 12:58                               ` Kanchan Joshi
2020-07-08 14:22                                 ` Matthew Wilcox
2020-07-08 16:41                                   ` Kanchan Joshi
2020-07-08 14:54                                 ` Jens Axboe
2020-07-08 14:58                                   ` Matthew Wilcox
2020-07-08 14:59                                     ` Jens Axboe
2020-07-08 15:02                                       ` Matthew Wilcox
2020-07-08 15:06                                         ` Jens Axboe
2020-07-08 16:08                                           ` Javier González
2020-07-08 16:33                                             ` Matthew Wilcox
2020-07-08 16:38                                               ` Jens Axboe
2020-07-08 17:13                                                 ` Kanchan Joshi
2020-07-08 16:43                                               ` Javier González
2020-07-06 13:58         ` Kanchan Joshi
2020-07-09 10:15         ` Christoph Hellwig
2020-07-09 13:58           ` Jens Axboe
2020-07-09 14:00             ` Christoph Hellwig
2020-07-09 14:05               ` Jens Axboe
2020-07-09 18:36                 ` Kanchan Joshi
2020-07-09 18:50                   ` Pavel Begunkov
2020-07-09 18:53                     ` Pavel Begunkov
2020-07-09 18:50                   ` Jens Axboe
2020-07-09 19:05                     ` Kanchan Joshi
2020-07-10 13:10                       ` Christoph Hellwig
2020-07-10 13:48                         ` Matthew Wilcox
2020-07-10 13:49                           ` Christoph Hellwig
2020-07-10 13:51                             ` Matthew Wilcox
2020-07-10 14:11                               ` Kanchan Joshi
2020-07-20 16:49                                 ` Kanchan Joshi
2020-07-20 17:14                                   ` Matthew Wilcox
2020-07-20 20:17                                     ` Kanchan Joshi
2020-07-21  0:59                                       ` Damien Le Moal
2020-07-21  1:15                                         ` Matthew Wilcox
2020-07-21  1:29                                           ` Jens Axboe
2020-07-21  2:19                                           ` Damien Le Moal
2020-07-10 14:09                         ` Jens Axboe
2020-07-20 16:46                           ` Kanchan Joshi
2020-07-10 13:09                     ` Christoph Hellwig
2020-07-10 13:29                       ` Kanchan Joshi
2020-07-10 13:43                         ` Christoph Hellwig
2020-07-20 17:02                           ` Kanchan Joshi
2020-07-10 13:57                         ` Kanchan Joshi

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