linux-kernel - Re: [RFC PATCH] request: teach the device more intelligent

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Date:	Wed, 10 Aug 2011 11:16:15 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Kyungmin Park <kmpark@...radead.org>
Cc:	Jens Axboe <axboe@...nel.dk>, jaxboe@...ionio.com,
	linux-kernel@...r.kernel.org, arnd@...db.de, jh80.chung@...sung.com
Subject: Re: [RFC PATCH] request: teach the device more intelligent

Kyungmin Park <kmpark@...radead.org> writes:

> Cc the correct email address of jens
>
> On Tue, Aug 9, 2011 at 12:47 PM, Kyungmin Park <kmpark@...radead.org> wrote:
>> Hi Jens
>>
>> Now eMMC device requires the upper layer information to improve the data
>> performance and reliability.
>>
>> . Context ID
>> Using the context information, it can sort out the data internally and improve the performance.
>> The main problem is that it's needed to define "What's the context".
>> Actually I expect cfq queue has own unique ID but it doesn't so decide to use the pid instead
>>
>> . Data Tag
>> Using the Data Tag (1-bit information), It writes the data at SLC area when it's hot data. So it can make the chip more reliable.
>> First I expect the REQ_META but current ext4 doesn't pass the WRITE_META. only use the READ_META. so it needs to investigate it.
>>
>> With these characteristics, it's helpful to teach the device. After some consideration. it's needed to pass out these information at request data structure.
>>
>> Can you give your opinions and does it proper fields at requests?
>>
>> Thank you,
>> Kyungmin Park
>> ---
>> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
>> index 1f96ad6..d73bfa7 100644
>> --- a/block/cfq-iosched.c
>> +++ b/block/cfq-iosched.c
>> @@ -3790,6 +3790,7 @@ new_queue:
>>        rq->elevator_private[0] = cic;
>>        rq->elevator_private[1] = cfqq;
>>        rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
>> +       rq->hint.context = (int) cfqq->pid;
>>        spin_unlock_irqrestore(q->queue_lock, flags);
>>        return 0;
>>
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index 0e67c45..0145c10 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -69,6 +69,14 @@ enum rq_cmd_type_bits {
>>        REQ_TYPE_ATA_PC,
>>  };
>>
>> +/*
>> + * request hint
>> + */
>> +struct request_hint {
>> +       int context;                    /* Context ID */
>> +       int hot:1;                      /* Hot/cold data */

This 1-bit member should be a type of unsigned?

Thanks.
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