Re: [9fans] 9p over high-latency
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Re: [9fans] 9p over high-latency         


Author: erik quanstrom
Date: Sep 18, 2008 05:02

> On Fri, Sep 12, 2008 at 7:47 PM, erik quanstrom quanstro.net> wrote:
>> as an aside: i don't think 9p itself limits plan 9 performance
>> over high-latency links. the limitations have more to do with
>> the number of outstanding messages, which is 1 in the mnt
>> driver.
>
> Hm, but what's the alternative here? Readahead seems somewhat
> attractive, if difficult (I worry about blocking reads and timing
> sensitive file systems). But there's one problem I can't resolve - how
> do you know what offset to Tread without consulting the previous
> Rread's count?
> Actually, I understand there has been discussion about grouping tags
> to allow for things like Twalk/Topen batching without waiting for
> Rwalk (which sounds like a great idea), maybe that would work here
> also...

the fundamental problem is that it becomes very difficult to
implement fileservers which don't serve up regular files.
you might make perminant changes to something stored on
a disk with readahead.
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Re: [9fans] 9p over high-latency         


Author: Eric Van Hensbergen
Date: Sep 18, 2008 06:38

On Thu, Sep 18, 2008 at 6:51 AM, erik quanstrom quanstro.net> wrote:
>> On Fri, Sep 12, 2008 at 7:47 PM, erik quanstrom quanstro.net> wrote:
>> also...
>
> the fundamental problem is that it becomes very difficult to
> implement fileservers which don't serve up regular files.
> you might make perminant changes to something stored on
> a disk with readahead.
>

My experience is that there are a couple of different scenarios here
-- there's dealing with synthetic file systems, dealing with regular
files, and then there is dealing with both. Latency can effect all
three situations -- my understanding was that Op was actually
developed to deal with latency problems in dealing with the deep
hierarchies of the Octopus synthetic file systems.
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