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From: Adam Manzanares <Adam.Manzanares@wdc.com>
To: Jens Axboe <axboe@kernel.dk>,
	"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
	"bcrl@kvack.org" <bcrl@kvack.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-aio@kvack.org" <linux-aio@kvack.org>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16
Date: Wed, 9 May 2018 15:29:00 +0000	[thread overview]
Message-ID: <a22de016-686f-ce93-c311-71a6719ee521@wdc.com> (raw)
In-Reply-To: <20180509152149.GG28388@thunk.org>



On 5/9/18 11:21 AM, Theodore Y. Ts'o wrote:
> On Wed, May 09, 2018 at 08:23:00AM -0600, Jens Axboe wrote:
>> Streams is essentially the only thing ki_hint is currently used for,
>> with the write life time hints mapping to a stream. The idea for the
>> user side API was to have other things than just write life time hints.
>>
>> Since Adam wants to do priorities, he'd either need to pack into the
>> existing ki_hint, or do this patch does, which is make it smaller and
>> add a new member. I think the latter is cleaner.
> 
> Fair enough; but maybe we can use a u8 instead of a u16?  65,535
> priorities still seem like way more than would ever make sense.  I
> think 256 priorities is still way to many, but it's simpler while
> still reserving number of bits for future se.

The intention was to mimic the ioprio_set system call, which uses 3 bits 
for a prio class and 13 bits for a prio_value.

IDK what is the right amount of bits to use, but the existing use of 
bits seemed flexible enough to support many types of applications and 
devices.
> 
>              		       	       	   - Ted
> 

  reply	other threads:[~2018-05-09 15:29 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-08 17:41 [PATCH v3 0/3] AIO add per-command iopriority adam.manzanares
2018-05-08 17:42 ` [PATCH v3 1/3] block: add ioprio_check_cap function adam.manzanares
2018-05-08 17:42 ` [PATCH v3 2/3] fs: Convert kiocb rw_hint from enum to u16 adam.manzanares
2018-05-09 13:34   ` Theodore Y. Ts'o
2018-05-09 14:23     ` Jens Axboe
2018-05-09 15:21       ` Theodore Y. Ts'o
2018-05-09 15:29         ` Adam Manzanares [this message]
2018-05-08 17:42 ` [PATCH v3 3/3] fs: Add aio iopriority support for block_dev adam.manzanares
2018-05-09  8:54   ` kbuild test robot

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