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Date: Fri, 10 Jun 2011 16:03:06 -0400
Message-ID: <BANLkTikbrBJL3K-v2Ecto1FfZ32QQwF8dw@mail.gmail.com>
Subject: Re: [PATCH 87/88] Add configurable prefetch size for layoutget
From: Fred Isaman <iisaman@netapp.com>
To: Benny Halevy <benny@tonian.com>
Cc: tao.peng@emc.com, bergwolf@gmail.com, rees@umich.edu,
        linux-nfs@vger.kernel.org, honey@citi.umich.edu
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On Fri, Jun 10, 2011 at 3:23 PM, Benny Halevy <benny@tonian.com> wrote:
>
> A simple algorithm I can suggest is:
> - on initialization, calculate and save, per layout driver
> ?- maximum layout size

I must be misunderstanding something.  Layout size has nothing to do
with io size (other than the obvious fact that you want the layout >
io).

I don't know about the object driver, but for both the file and block
drivers the client wants as much as the server will give it.

Fred

> ? ?- take into account csr_fore_chan_attrs.ca_maxresponsesize and possible other parameters
> ?- keep a working copy of the maximum value and the calculated copy.
> ?- alignment value.
> - on miss, see if there's an adjacent layout segment in cache
> - if found, ask for twice the found segment size, up to the maximum value,
> ?aligned on the alignment value.
> - if the server returns less the layoutget range, keep note of the returned length
> ?(but not adjust maximum yet, as the server may return a short segment for various
> ? reasons)
> - if the server is consistent about returning less than was asked, adjust the
> ?- working copy of the maximum length
> - if the maximum was adjusted try bumping it up after X (TBD) layoutgets or T seconds
> ?to see if that was just due to high load or conflicts on the server
> - on any error returned for LAYOUTGET reset the algorithm parameters
> - on session reestablishment recalculate maximums.
>
> Benny
>