linux-kernel - Re: [PATCH V7 1/4] blk-mq: refactor the code of issue request directly

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Message-ID: <17b51550-d45b-9861-b172-74ee0e256d98@oracle.com>
Date:   Wed, 14 Nov 2018 17:23:48 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V7 1/4] blk-mq: refactor the code of issue request
 directly

Hi Ming

On 11/14/18 5:11 PM, Ming Lei wrote:
>>  
>> -	if (!blk_mq_get_dispatch_budget(hctx))
>> -		goto insert;
>> +	if (unlikely(!blk_mq_get_dispatch_budget(hctx)))
>> +		goto out_unlock;
> The unlikely annotation is a bit misleading, since out-of-budget can
> happen frequently in case of low queue depth, and there are lots of
> such examples.
> 

This could be good for the case for no .get_budget and getting budget success.
In case of out-of-budget, we insert the request which is slow path.
It should be OK. Maybe some comment should be added for this.

Thanks
Jianchao