From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 1/2] block: support different tag allocation policy
Date: Mon, 15 Dec 2014 00:08:13 -0800
Message-ID: <20141215080813.GA3982@infradead.org>
References: <e0ea802ef0d4170ad409e5dbf814c28581c091ac.1418613253.git.shli@fb.com>
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To: Shaohua Li <shli@fb.com>
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On Sun, Dec 14, 2014 at 07:21:49PM -0800, Shaohua Li wrote:
> The libata tag allocation is using a round-robin policy. Next patch will
> make libata use block generic tag allocation, so let's add a policy to
> tag allocation.
> 
> Currently two policies: FIFO (default) and round-robin.

What's the benefit of round robin allocation?  Why do you only need
it for the old simple allocator, and no policy control for the more
complex blkpmq allocator?