From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <jianchao.w.wang@oracle.com>
Subject: Re: [RFC PATCH V2 04/17] blk-mq: don't reserve tags for admin queue
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Alan Stern <stern@rowland.harvard.edu>, Christoph Hellwig <hch@lst.de>,
        Bart Van Assche <bart.vanassche@wdc.com>,
        Hannes Reinecke <hare@suse.de>,
        Johannes Thumshirn <jthumshirn@suse.de>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org
References: <20180811071220.357-1-ming.lei@redhat.com>
 <20180811071220.357-5-ming.lei@redhat.com>
 <14c6e892-b05f-7422-0fd3-da45a645d3ba@oracle.com>
 <20180813104822.GA18557@ming.t460p>
From: "jianchao.wang" <jianchao.w.wang@oracle.com>
Message-ID: <85e5fb60-fdf1-436e-8bc1-5480d5b2b17f@oracle.com>
Date: Tue, 14 Aug 2018 09:29:25 +0800
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In-Reply-To: <20180813104822.GA18557@ming.t460p>
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List-ID: <linux-block@vger.kernel.org>

Hi Ming

On 08/13/2018 06:48 PM, Ming Lei wrote:
> It is nothing to do with where the admin request is sent, so no any
> difference wrt. this issue between with and without this patchset,
> right?

I'm afraid not.

For example:
  A scsi host has 8 LUNs associated with it.
  Before this patch set,
  When we send out the admin command, the budget is _per_ LUN, 1/8 of the total tags.
  After this patch set,
  When we send out the admin command, the budget is equal to _one_ LUN, 1/8 of the total tags.

However, the 1/8 above is different.
  Before the patch set, every LUN's admin command has 1/8 budget to use which is per LUN.
  After this patch set, all the 8 LUNs admin command has to share the 1/8 budget.


Thanks
Jianchao