Date: Tue, 29 Mar 2016 09:47:23 -0700
From: Shaohua Li <shli@fb.com>
To: Christoph Hellwig <hch@infradead.org>
CC: <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <axboe@fb.com>, <Kernel-team@fb.com>
Subject: Re: [PATCH 1/3] blk-mq: add an API to estimate hardware queue node
Message-ID: <20160329164722.GA1208161@devbig084.prn1.facebook.com>
References: <68fed570910230ce847f8f3b685eeea399640a7f.1458941500.git.shli@fb.com>
 <20160329072443.GA18920@infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <20160329072443.GA18920@infradead.org>
User-Agent: Mutt/1.5.20 (2009-12-10)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 875
Lines: 15

On Tue, Mar 29, 2016 at 12:24:43AM -0700, Christoph Hellwig wrote:
> On Fri, Mar 25, 2016 at 02:36:30PM -0700, Shaohua Li wrote:
> > we allocate most data structure in device's node, but some data
> > structures are not for DMA and mostly used by specific cpus/node which
> > could diff from device's node. Allocating such hot data in device's
> > node doesn't make sense. Add an API to estimate hardware queue node.
> > This can be used before blk-mq actually establishes the mapping. This
> > API runs slow, but it only used in initialization time.
> 
> I think this is the wrong way around.  I've got some proprotype code
> that just leaves the cpu assignments to the drivers and picks it up
> in blk-mq.  Give me a few days to post it..

This looks weird, shouldn't the cpu assignment be determined by block
core (blk-mq) because block core decides how to use the queue?